DIAGNOSTIC TOOL FOR HIGHER LEVEL PROTOCOL TESTING ON A TCP/IP BASED NETWORK FAISAL ASLAM

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DIAGNOSTIC TOOL FOR HIGHER LEVEL PROTOCOL

TESTING ON A TCP/IP BASED NETWORK

FAISAL ASLAM

submitted in partial fulfilment of the requirements of

Napier University for the degree of

Bachelor of Engineering with Honours in Software

Engineering

School of Computing

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Abstract

The aim of this project is to design and implement a system, which will test session layer protocols. Protocols are used for communicating between software packages.

The software will contain a Client and Server architecture to test the protocols over a network. The project will use Transmission Control Protocol/Internet Protocol (TCP/IP) protocols, such as File Transfer Protocol (FTP), Simple Mail Transfer Protocol (SMTP), Hypertext Transfer

Protocol and the terminal emulation protocol, Telnet.

This report will test the connection and protocols using a Client and Server architecture. This report provides a step-by-step explanation of TCP/IP theory, design, test and

implementation. Instead of just describing the protocols and what they do, a diagnostic tool will be developed to watch the protocols in action. This project also provides a look into the

implementation of the protocols, without having to go through thousands of lines of source code.

Many people might consider this tool to be used for diagnosing network problems, but it is also a powerful tool for understanding how the network protocols operate.

The test system will use a client/server architecture, where the device on-test will act as the client, and the other program will act as a server. Each client will make requests for a given protocol to the server, which will respond with a basic set of responses.

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Connect Event...16 Close Event...16 DataArrival event...16 Bind method...16 Listen method ...17 2.8 Conclusion ...17 3 Design ...18 3.1 Introduction...18 3.1.1 Specification ...18 3.1.2 Purpose ...18 3.1.2 Hardware...18 3.1.3 Quality Goals ...18 3.1.4 Portability ...18 3.1.5 Efficiency...18 3.1.6 Reliability ...19 3.1.7 Maintainability...19 3.1.8 Usability...19 3.1.9 Functionality ...19 3.2 Project Requirements...19

3.2.1 Project Specific Requirements...19

3.2.2 Specific areas of exclusions from the project ...19

Client/Server Design...19

3.2.4 Client/Server ...19

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3.3.1Designing the Client ...20

Server Design...21

3.4 Designing the Server...22

3.4 Conclusion ...22 4 Testing ...24 4.1 Introduction...24 4.2 Test Plan ...24 Problems ...25 Initialisation ...25

Read codes from servers ...25

4.3 Conclusion ...25 5 Implementation ...26 5.1 Introduction...26 5.2 FTP Implementation ...26 5.3 SMTP Implementation...27 5.4 TCP Implementation...29 5.6 Conclusion ...30 6 Conclusion ...31 Appendix 1...32

Documentation and Screen Shots ...32

Appendix 2...33 RFC’s...33 Appendix 3...34 Source Code...34 References...50 Bibliography ...51

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Acknowledgements

I would like to thank Dr. W Buchanan my project supervisor for all the support and

encouragement he gave to this project and also of the subject provided and the great interest and purpose of it.

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1 Introduction

1.1 Aims and Objectives

The goal of this project is to implement and design a system, which will test session layer protocols. The aims are to design and implement some of the test session layer protocols such as SMTP, Telnet, FTP and HTTP. This will be achieved by researching RFC documents such as RFC822. There will also be a need to implement a Client/Server architecture using TCP/IP. The project is split into these main areas:

Research

Defining each of the TCP/IP protocols from RFC documents, such as RFC821 which defines the SMTP protocol (e-mail), RFC2068 (HTTP), and so on.

Set-up of a client/server program

This will set-up a basic text-based connection between the client and the server, and will test the link over a network.

Implementation of a basic set of protocols

This will be the investigation of the implementation into one or more of the TCP/IP.

Full design

This will use the research and implementation parts to develop the design for a full system.

Prototype (partial implementation)

This will take part of the full design and implement it as a partial implementation

Project write-up

Defines the main objectives of the project, cover the theory of TCP/IP and show the implementation of the protocols, a full design and outline the developed prototype.

1.2 Report Layout

The report is split into the five following chapters, and will be laid out as follows.

• Chapter 2 describes the theory of TCP/IP and Networking. The OSI model will be discussed in detail. This will provide a clearer understanding of what is required from the implementation of the protocols. This will also show the background on how the software will operate. Session Layer protocols will also be discussed as will Object Oriented Design and the Visual Basic Winsock. This whole chapter will give a background to the fundamentals of Networking. Defining each of the TCP/IP protocols from RFC documents, such as RFC821, which defines the SMTP protocol (e-mail), RFC2068 (HTTP), and so on will also be covered.

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• Chapter 3 is concerned with the design side of the project. It will give an insight into the Client/Server Architecture and also the investigation into the Session Layer. Issues such as software design and architectures will be covered. This will use the research and implementation parts to develop the design for a full system. This will set-up a basic text-based connection between the client and the server, and will test the link over a network.

• Chapter 4 will illustrate the Testing. It will show testing on Protocols, which have been implemented.

• Chapter 5 discusses the implementation of the design. This looks into the various implemented protocols and Visual Basic. It will show the Implementation of the various protocols and the errors encountered.

• Chapter 6 is the summary of the conclusions reached in the project.

1.3 Background

TCP/IP (Transmission Control Protocol/Internet Control Protocol) has become a phenomenally popular network protocol. Today most networks are TCP/IP based. The growth of the Internet has helped push TCP/IP to the forefront of network protocols.

With the explosive growth of the World Wide Web, every computer now needs to understand TCP/IP in order to talk to an Internet service provider. TCP/IP is one of the most stable network protocols available. The start of the project involved research into each of the TCP/IP protocols from the RFC documents, such as RFC821 which defines the SMTP protocol (email), RFC2068 (HTTP), and so on. This involved a lot of reading. Also to find a way to create a Client and a Server. The Client/Server also had to connect to a Server like the Department of Computer Studies of Napier University, and find the different protocols to communicate with it. Visual Basic 6 was chosen to make the program because the manipulation of the ports is quite easy in this language.

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2 Theory

2.1 Introduction

Today nearly all computers in companies are networked together. This allows an effective way of communication among the workforce. Email and the Internet are the two most popular network systems. People can communicate instantly across the world in real time. Everything from printers to disks can be shared, regardless of its geographical location.

For a network to operate effectively, the computers must speak the same language. This is where the network protocols come in. These are basically the set of rules that allow to computers or many more to communicate with each other. One of the most important protocol is called the Transmission Control Protocol TCP/IP, which is the most standard protocol, which computers use to connect. It allows access to the Internet and a new world of communication. TCP/IP has been the most successful communications protocol ever built. Evidence of this is found on the Internet, as this is the largest open network ever built. It allows all computers regardless of size, or operating systems to communicate with each other.

This section covers the basics of networking and the OSI model. It also covers TCP/IP and the session layer protocols. It will describe the theory of TCP/IP and Networking. The OSI model will be discussed in detail. This will provide a clearer understanding of what is required from the implementation of the protocols. Session Layer protocols will also be discussed as will Object Oriented Design and the Visual Basic Winsock. This whole chapter will give a background to the fundamentals of Networking. Defining each of the TCP/IP protocols from RFC documents, such as RFC821, which defines the SMTP protocol (e-mail), RFC2068 (HTTP), and so on will be covered.

2.1.1 Networking/OSI

2.2.1 Networking History

The Internet was specifically designed to facilitate defence research, and to enable the U.S. Government to continue communications despite the potentially devastating effects of a nuclear attack. TCP/IP was developed for this purpose. It all started up with the ARPANET (The Advanced Research Projects Agency) which at the time was looking for ways to improve communications. The first protocol developed was called the Network Control Protocol (NCP), but as network traffic got larger NCP was unable to cope. After the birth of ARPANET, Vinton Cerf and Robert Kahn invented the Transmission Control Protocol (TCP) which replaced the NCP. The result was the Internet being born [1].

Today the Internet is no longer just used for Military or academic research. Everyone on the Internet can shop and bank online. The various uses of the Internet are endless.

In 1969 the ARPANET started with four nodes and grew to just under 600 before it was split in 1983. According to an Internet Growth survey, the Internet had nearly 30 million reachable hosts

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by January 1998. The Internet is growing at a rate of about a new network attachment every half-hour, interconnecting more than 200,000 networks [2].

2.2 The OSI model

In today’s electronics and computers, there are a lot of problems with compatibility and interconnection. This includes connecting computers together, which are located at various points around the world. The International Standards Organisation (ISO) built the OSI model, which would allow:

• Any kind of computer system, regardless of the manufacturer to interconnect.

• Any type of software and hardware would be compatible.

• This model would be like a rule and regulation for the entire world.

There are seven layers in this OSI model. Data is passed from the top layer (the application layer) by the sender to the bottom layer (the physical layer) and then back up to the top layer by the recipient. Each layer can communicate with the preceding layers which allows data flow amongst the layers.

The application layer receives data from an application and then adds data, which recipient’s application layer will then receive. The data that is added is passed on to the next layer, which is called the presentation layer. Here also data is added until you eventually get to the physical layer. The physical layer has to transmit the data to the recipient. The data which is sent by the network or the transport layer is called a data packet.

Below are the characteristics of each layer:

1. Physical Layer, states the electrical functions. This is the bottom layer. This layer is responsible for the transmission of the bit stream. It accepts these frames of data from the Data Link layer. It deals with all the signals like voltage levels, connecters and cabling etc. The Physical Layer only sees 1s and 0s. The Physical Layer is also responsible for the reception of incoming data streams, one bit at a time.

2. Data Link Layer, this is the second layer of the OSI Model. Like all the other layers this

layer too has two sets of responsibilities. These are to transmit and to receive. It ensures that all data is received in a reliable fashion. Successful delivery means that the frame reaches its intended destination intact. It achieves this by adding additional bits to illustrate the start and the finish of the data frame. The Data Link Layer is responsible for detecting and correcting any errors.

3. Network Layer, is responsible for establishing the route to be used between the host and

destination computers. It routes all data frames through the network. In TCP/IP the IP is directly involved with this layer.

4. Transport Layer, this layer provides a service very similar to the Data Link Layer as it

also is responsible for the see through of the transmissions. It allows multiple transmissions from one computer. The TCP is directly involved with this layer.

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5. Session Layer, this layer likely unused most of the time. The function of this layer is to

manage the flow of communications during a connection between two computer systems. This flow of communications is known as a session. It ensures that one request is completed before a new one is taken on. A protocol which is typically related to this layer in many ways, is Telnet.

6. Presentation Layer, is responsible for managing the way that data is encoded. If systems

use different standards, this layer is responsible for providing the translation between these systems. It can also provide security encryption and decryption services.

7. Application Layer, this is the very top layer of the OSI model. It provides the network

services to application programs. This can be like FTP and SMTP.

2.3 TCP/IP

Transmission Control Protocol/Internet Protocol (TCP/IP) is everywhere. It can be at any place at any time. It’s a set of protocols which allow anyone with a computer to communicate with another. Both TCP and IP are two separate protocols that work together and distribute data packets reliably over the Internet. They both use special headers that define each packets content. TCP makes itself busy by making connections to remote hosts. IP deals with the addressing so that messages are delivered to where they are intended for. The Internet uses TCP/IP to transfer data.

2.3.1 TCP

Transmission Control Protocol (TCP) is a protocol which provides a reliable stream delivery and connection to applications. TCP is the transport layer in the OSI model. TCP establishes a connection-oriented session between two or more hosts. It can also provide multiple data streams as well as flow and error control.

TCP provides many important functions in a communications session. It can be thought of the relation between the multiple applications and the network. These are its main functions:

• Multiplexing data from multiple applications to and from networks.

• Testing received data

• Resequencing application data that may have arrived in the wrong order.

• Acknowledging successful receipt of transmitted data.

• Flow control

• Timing functions

• Coordinating the retransmissions of data that was damaged or lost in transit. These are the parts of the TCP header:

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• Source Port. This is the numerical value indicating the source port.

• Destination Port. This is the numerical value indicating the destination port.

• Sequence Number. This is the sequence number of the first data octet in any given segment.

• Acknowledgment Number (ACK). When the ACK bit is set, this field contains the next

sequence number that the sender of the segment is expecting to receive.

• Data Offset. This is the numerical value that indicates where the data begins, implying the

end of the header by offset.

• Reserved. Reserved is not used.

• Control Bits. The control bits are: U(URG), A(ACK), P(PSH), R(RST), S(SYN), F(FIN)

• Window. This indicates the number of octets the sender is willing to take. This starts with

the packet in the ACK field.

• Urgent (URG) Pointer. This shows the value of the URG pointer in the form of a positive

offset of the sequence number from the octet that follows the URG data.

2.3.2 TCP/IP Applications

The TCP/IP Application Layer protocols support the applications and utilities that are the Internet. Commonly used protocols are as follows:

• Telnet: Short for Telecommunication Network, a virtual terminal protocol allowing a user

logged on to one TCP/IP host to access other hosts on the network RFC 854 [5].

• FTP: The File Transfer Protocol allows a user to transfer files between local and remote

host computers RFC 959 [6].

• SMTP: The Simple Mail Transfer Protocol is the standard protocol for the exchange of

electronic mail over the Internet RFC 821. SMTP is used between e-mail servers on the Internet or to allow an e-mail client to send mail to a server. RFC 822 specifically describes the mail message body format, and RFCs 1521 and 1522 describe MIME (Multipurpose Internet Mail Extensions) [8].

• HTTP: The Hypertext Transfer Protocol is the basis for exchange of information over the

World Wide Web (WWW). Various versions of HTTP are in use over the Internet, with HTTP version 1.0 RFC 1945 being the most current. WWW pages are written in the Hypertext Markup Language (HTML), an ASCII-based, platform-independent formatting language RFC 1866 [9].

2.3.3 Layers

Protocols are usually developed in layers, each layer being responsible for a different level of the communications. TCP/IP is a variety of protocols at different layers. There are four layers of the TCP/IP protocol suite.

• The Link Layer. This layer is also known as the data-link layer or network interface layer.

This includes the device driver in the operating system and also the network interface card in the computer. This layer handles all the hardware details.

• The Network Layer. This layer is also known as the Internet layer. It deals with the

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includes IP (Internet Protocol), ICMP (Internet Control Message Protocol), and IGMP (Internet Group Management Protocol).

• The Transport Layer. This layer provides the flow of data between two hosts, for the

application layer above. In the TCP/IP protocol suite there are two different transport protocols: TCP (Transmission Control Protocol) and UDP (User Data-gram Protocol).

• The Application Layer. This layer handles the details of the particular application. It

consists of SMTP, FTP, NFS, Telnet and Remote Login.

• Transmission Control Protocol (TCP). The Transmission Control Protocol (TCP) is a

protocol that provides a reliable stream delivery and connection service to applications. TCP uses sequenced acknowledgement and is able to retransmit packets as needed. TCP is described in RFC 793 and is the basic communication language or protocol of the Internet.

2.4 IP

The Internet Layer Protocol (IP) manages how packets are delivered to and from servers and clients. It is probably the most dominant internetworking protocol in the world. These are its main functions:

• Addressing and routing – it enables packets to be delivered to a specific destination. IP knows the location of the gateway on the network. The gateway then interconnects the network. There after data is passed from the node to the gateway.

• Fragmentation and reassembly – sometimes segments of applications do not fit inside an IP packet, due to this they are fragmented.

• Detection and correction of data damaged in transit – the node which detects the error reports this to the source node. A packet could also be lost and again an error message will be submitted. It will also return an error if the network does not exist.

2.4.1 IP Addresses and Host Names

When a system is part of a TCP/IP network, it needs to have an identification address. This address, called the IP or Internet Protocol address, is a 32-bit number that is usually represented by four numbers separated by periods. An example is 190.137.48.1. This is the decimal representation of four bytes. When assigned to your computer, this number is its node address, whether your system is attached to the Internet, to your company LAN, or to a system of two computers at home that you have attached in a small local LAN.

2.5 Ports

The TCP/IP protocol is used for communication between computer systems. Port numbers are used for communicating between applications on the two systems. Ports are also called sockets. This is the origin of the Winsock terminology.

When two applications are communicating by using the TCP/IP protocol, the applications use port numbers to identify themselves to the other application. When a server receives a request for a connection, the request is directed to a particular TCP/IP port. The server then knows which application is being contacted because it has the port number associated with the application. This is analogous is like having two phones in your house, one for business and one for personal use. Servers listen on a particular port, and clients send requests to that port. In the everyday world of Internet usage, there are well known ports. Some of these ports have become standard. The World Wide Web uses Port 80, and FTP uses Port 21. WWW would function just as well on

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Port 37, but everyone has agreed that Port 80 will be used. This is similar to the use of 999 for an emergency phone number.

A particular server application listens on a specific port number for requests to connect to that server. If you have a system that is used for both WWW and FTP, it will listen on both Ports 21 and 80. If the request for connection comes in on Port 80, the Web server application handles the communication.

Having a system work as a server for one application does not prevent it from being a client for another application. A system can be a Web server listening on Port 80 and communicate contemporaneously with another system on another Port for a different application.

An important point to remember is that the client system does not have to send the request for service from the same port on which the server is listening. For example, if the server ABC application is listening on Port 239, the client may send its request for service from its Port 1593 to the server's Port 239. This works because the client tells the server the port number that its request came from, so the server responds to the client by sending the response to Port 1593. The essential parts of the message sent from one computer system to another are the following:

• Destination IP Address This is a dotted quartet for example, 191.187.39.55. This is how

the network identifies the node of the network for which the message is bound.

• Origin IP Address This is also a dotted quartet; it is used if any replies or requests for

retransmission are required.

• Destination Port Number This identifies the socket for which the message is bound.

Because sockets or ports are linked or bound to one application, this is the "address" of the application on the system.

• Origination Port Number This is used for any replies that are sent to the originating

system to identify to the TCP/IP protocol. This application is the intended recipient of the message.

• Data This is the information that the applications are sending to each other.

2.6 Protocols

2.6.1 SMTP (Simple Mail Transfer Protocol)

SMTP (Simple Mail Transfer Protocol) is a TCP/IP protocol used in sending and receiving E-mail. However, since it's limited in its ability to queue messages at the receiving end, it's usually used with one of two other protocols, POP3 or IMAP that let the user save messages in a server mailbox and download them periodically from the server. In other words, users typically use a program that uses SMTP for sending E-mail and either POP3 or IMAP for receiving messages that have been received for them at their local server. SMTP usually is implemented to operate over TCP port 25. The details of SMTP are in RFC 821 of the Internet Engineering Task Force (IETF).

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2.6.2 Telnet

Telnet is the way to access someone else's computer, assuming they have given permission. (Such a computer is frequently called a host computer.) More technically, Telnet is a user command and an underlying TCP/IP protocol for accessing remote computers. The Web or HTTP protocol and the FTP protocol allow to request specific files from remote computers, but not to actually be logged on as a user of that computer. With Telnet, it is necessary to log on as a regular user with whatever privileges granted to the specific applications and data on that computer.

The result of a request would be an invitation to log on with a userid and a prompt for a password. If accepted, the remote user would be logged on like any user who used this computer every day.

Telnet is most likely to be used by program developers and anyone who has a need to use specific applications or data located at a particular host computer.

2.6.3 File Transfer Protocol (FTP)

FTP is the TCP protocol that is widely used to transfer files. There are two types of connections established in an FTP session: a control connection and a data connection.

FTP (File Transfer Protocol), a standard Internet protocol, is the simplest way to exchange files between computers on the Internet. Like the Hypertext Transfer Protocol (HTTP), which transfers displayable Web pages and related files, and the Simple Mail Transfer Protocol (SMTP), which transfers e-mail, FTP is an application protocol that uses the Internet’s TCP/IP protocols. FTP is commonly used to transfer Web page files from their creator to the computer that acts as their server for everyone on the Internet. It's also commonly used to download programs and other files to your computer from other servers.

As a user, you can use FTP with a simple command line interface (for example, from the Windows MS-DOS Prompt window) or with a commercial program that offers a graphical user interface. Web browsers can also make FTP requests to download the selected programs from a Web page. Using FTP, it is possible to update (delete, rename, move, and copy) files at a server. It is necessary to log on to an FTP server. However, publicly available files are easily accessed using anonymous FTP.

Basic FTP support is usually provided as part of a suite of programs that come with TCP/IP. However, any FTP client program with a graphical user interface usually must be downloaded from the company that makes it.

Control Connection The control connection, which is maintained throughout the FTP session, is

used to transmit commands between the client and the server. The first step in the FTP session process consists of the server listening on FTP's well-known port, Port 21. The FTP server listens by performing a passive open of a control connection, which waits for an active open control connection request.

The second step in the FTP session process consists of the client sending an active open control connection request to the FTP server, which request is addressed to Port 21. If all of the logon requirements are met, an active control connection is created between the client and the server.

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This connection stays open throughout the FTP session. Commands and replies are communicated over this connection.

Data Connection A data connection is established each time a file is transferred and is

maintained only so long as the file transfer is in process. The client establishes a data connection to either upload or download a file. When the file has been transferred, the data connection is terminated.

When the client is finished with the FTP session, a command terminating the control connection is sent to the server and the FTP session is terminated.

2.6.4 Hypertext Transfer Protocol (HTTP)

HTTP is one of the protocols that uses the basis of TCP/IP in a specific implementation. This is the protocol of the World Wide Web. HTTP currently is in version 1.0 and moving toward version 1.1. Most Web servers will be updated in the near future to support 1.1, as will Web browsers. There will be backward compatibility for both servers and browsers. HTTP is a very simple protocol. The client, usually called a browser, issues a request to the server. The server responds with the requested file and closes the connection.

There are two HTTP message types: requests and responses. There are three types of requests: GET, HEAD, and POST. In a GET request, a file is requested. In a HEAD request, only the server header information is returned. In a POST request, the BODY is transmitted to the server, and it contains data such as an HTTP form or a MAIL message.

HTTP Request The format of an HTTP request is the following:

request-line

headers (0 or more) <blank line>

body (only for POST requests) The format of the request-line is: request request-URL HTTP/Version An example of a request-line is: GET /afile.htm HTTP/1.0

HTTP Response The format of the HTTP response is:

status-line

headers (0 or more) <blank line> body

The body usually will be an html file that contains formatting tags and links that are used in other requests. The format of the status-line is:

HTTP/version response-code response-phrase An example of a status-line is:

HTTP/1.0 200 OK

There are a number of other status codes. If you have spent any time on the Web, you have seen the 404 Not Found response.

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2.7 Object Oriented Design

For this project Visual Basic was chosen as it allowed the controlling of a computer quite easily, this is referred to as socket programming. It is relatively easy to build complex applications with Visual Basic.

2.8 Visual Basic WinSock

Visual Basic has a WinSock control which allows the connection of hosts in a network. It does support TCP. The object of this WinSock has these properties like:

Obj.RemoteHost – this shows the IP address or the domain name Obj.LocalPort – this shows the local port number

These are the methods that are used with the WinSock Object:

Obj.Connect – Connects to a remote host Obj.Listen – Listens for a connection

Obj.GetData – Reads data from the input stream

Obj.SendData – Sends data to an output stream

These are the main events:

ConnectionRequest – when a remote host wants to make a connection with a server DataArrival – when data has arrived from a connection

It is also possible in Visual Basic to have multiple connections to the server. Every time there is a new connection a new one will be created.

These are events and methods used in the program:

Connect Event

This event connects to a server.

Private Sub Object.Connect (ErrorOccurred As Boolean)

Close Event

This event occurs when the remote computer closes the connection.

Object_Close()

DataArrival event

This event occurs when new data is received and the number of bytes returns.

Object_DataArrival (bytesTotal As Long)

Bind method

This specifies the local port and the IP address which used in TCP connections.

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Listen method

This creates a socket and activates the listen command.

Object.Listen

Accept method

This accepts incoming connections after an event.

Object.Accept requestID

Close method

This closes the TCP connection.

Object.Close

SendData method

This sends data to a remote computer.

Object.SendData

GetData method

This gets data from an object.

Object.GetData

2.8 Conclusion

This chapter has described all the basics of networking including the OSI model. These seven layers are crucial to the entire model. TCP/IP protocols interact with these layers at different levels in the model. TCP/IP is an amazing protocol as it can be run over many computers on a network. As networks are always expanding TCP/IP has been able to cope with this demand very well.

Using TCP/IP any person in the world regardless of their location can communicate freely with another person on a computer. Resources can be shared like printers and disks.

As you can see from this chapter there are many technical aspects related to the movement of packets across a network. That’s the reason why TCP and IP are joined so closely together. Each of them have critical jobs to perform and to a high standard. TCP/IP is very reliable.

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3 Design

3.1 Introduction

This section describes the requirements that the system will be expected to achieve. This will show exactly what is required of the software but will not show how the solution will be implemented.

3.1.1 Specification

3.1.2 Purpose

The demonstration program will show how the implementation of the protocols is achieved. The implementation will comprise of a Server program and a Client program. For this demonstration, only one Client will be given access to the Server at one time. The Client will have the ability to terminate the Server remotely.

3.1.2 Hardware

This program has been designed to be hardware independent, that is with the configuration has been designed to run on any system that supports sockets. The system also has to have Internet connectivity to allow use of the sockets and TCP, which the program requires.

3.1.3 Quality Goals

Quality goals have been based around McCall’s1 model

3.1.4 Portability

Portability has been built into the project in that it is adaptable to any other system that supports the software requirements of the project. It is easy when compiled to install it onto the system required. It will also conform to set standards of portability.

3.1.5 Efficiency

Efficiency, this applies to all resources that system uses, hardware, software, personnel and any other resource the system uses.

The result of the project must be fit for the purpose for which it was intended. The specification must be satisfied.

This project has not been optimised for performance but will work on an acceptable time frame for the users.

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3.1.6 Reliability

Reliability, this means the system must be relied on, and must be sound and consistent whenever used. This does not take into effect off the ground between the Client and Server. The Internet has its own built in problems with regard to reliability and is beyond the scope of this project.

3.1.7 Maintainability

Maintainability as most of this program is concrete and well documented it should pose little difficulty in maintenance. The parts that are maintainable are the Client/Server side of things. It will also be easy to upgrade.

3.1.8 Usability

Usability, applies to all programs, if they cannot be used for the purpose which they are designed then the wrong product has been built. Usability will cover the speed of response for the user, as well ease of use.

3.1.9 Functionality

Functionality, in this project will meet the requirements laid down in this specification

document. The needs of the project are laid down at the beginning of this document under the title purpose.

3.2 Project Requirements

3.2.1 Project Specific Requirements

This document lays down the specific goals of the project, addressing only the issues covered here. For the demonstration of the implementation into one or more of the TCP/IP protocols. With these goals implemented, you can communicate with any given TCP/IP protocol. The Client will make requests for a given protocol to the server, which will respond with a basic set of responses.

3.2.2 Specific areas of exclusions from the project

Only a few protocols will be implemented as there are virtually thousands of protocols in the RFC documents.

Client/Server Design

This document lays down the stages of this design, these are getting the vehicle of the project designed. That is the Client/Server initial protocol program. The requirements will be met, if implemented correctly.

3.2.4 Client/Server

Client/server describes the relationship between two computer programs in which one program, the client, makes a service request from another program, the server, which fulfils the request. ln a network, the client/server model provides a convenient way to interconnect programs that are distributed efficiently across different locations. Computer transactions using the client/server model are very common.

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The client/server model has become one of the central ideas of network computing. Most business applications being written today use the client/server model. So does the Internet's main program, TCP/IP. In marketing, the term has been used to distinguish distributed computing by smaller dispersed computers from the "monolithic" centralised computing of mainframe computers. But this distinction has largely disappeared as mainframes and their applications have also turned to the client/server model and become part of network computing.

In the usual client/server model, one server is activated and awaits client requests. Typically, multiple client programs share the services of a common server program. Both client programs and server programs are often part of a larger program or application. A computer with TCP/IP installed allows making client requests for files from File Transfer Protocol (FTP) servers in other computers on the Internet.

TCP/IP is not merely a pair of communication protocols but is a suite of protocols, applications and utilities. Increasingly these protocols are referred to as the Internet Protocol Suite.

3.3 Client/Server Design

The Client/Server paradigm was chosen to meet the needs of a distributed computing environment. It should appear as if it was a non-distributed application. The Client/Server paradigm belongs to the Application layer in the OSI model as peer to peer communication. In this demonstration, the Server will be limited to processing one Client at a time for simplicity. The server is TCP based and this allows you to establish end to end connection between the two communicating hosts. TCP provides reliability with a mechanism called Positive Acknowledgement with Retransmission (PAR). A system using PAR sends the data again, unless it hears from the remote system that the data arrived okay. The control is handled by a three-way handshake. A unit of data sent between Client and the Server is called a segment.

The Client always initiates the conversation, and the server must provide appropriate answers. At any point, if either party does not keep the exchange going, the connection is broken and the conversation ends. If the conversation ends without the proper cleanup, the conversation cannot be reinitiated until the applications have been reset.

3.3.1Designing the Client

When designing this sample client application, the user would want to see messages and replies in two separate text boxes. RichTextBoxes were selected because of their capability to use text formatting, and these text boxes were designated InBound and OutBound. A command button was added to initiate the connection.

Two more text boxes were added to enter the remote host name or IP address and the remote port, which enables the host and port to be selected and set at run time.

A final text box was added to display the local port number. This local port number can be read before the connection is created and after the connection is made.

And last, but certainly not least, a Microsoft Winsock Control 6.0 is added. This Winsock Control manages the communications between the client and server systems.

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Client Design

What the Client has to do

1. Use Transmission Control Protocol (TCP). 2. Be able to connect to the Server.

3. Be able to terminate its session with the Server.

4. Allow a Client to terminate its session and terminate the Server.

How the Client communicates with the Server

The Client has the job of sending requests to the Server and waiting for a reply. To carry out these communications tasks the Client uses the TCP/IP socket interface.

Sequence of calls made by the Client using TCP

1. Create a socket and connect to the Server via IP address.

2. Write to the Server a request until the user requests a quit selected. 3. Read back the response from your request then repeat write read cycle. Close the socket when finished with the service.

Laying Out the Form

When the application runs, you need to enter the remote host name or IP address and the remote port number before clicking the Connect button. After the connection is established, you can enter text in the Outbound Text box. When entered, text is automatically dispatched to the Server application. When you enter a character in the Outbound text box, a change event is triggered, and its attached event handler sends the contents of the text box to the remote host.

Server Design

What the Server has to do.

1. Use Transmission Control Protocol (TCP).

2. Respond to one Client at a time, this makes the Server Iterative. 3. Allow a Client to terminate its session.

4. Allow a Client to terminate its session and terminate the Server.

How the Server communicates with the Client

The Server has the job of responding to a Client, this means that the Server has to wait for a Client to make a contact, carry out a command and respond with an answer to the Client.

To carry out these communications tasks the Server uses the TCP/IP socket interface.

Sequence of calls made by the iterative Server using TCP

1. Create a master socket and bind to the well-known address for the service being offered.

2. Make the Server ready for use.

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4. Repeatedly read a request from the Client, formulate a response, and send a reply back to the Client according to the application protocol.

3.4 Designing the Server

When the sample server application was designed, the primary requirement was that the application be capable of servicing the needs of the client application. The server application looks like a mirror image of the client application, with the exception that it cannot initiate a connection.

The users see their messages and the replies in two separate text boxes. A text box is added to display the Remote Port number. This enables you to see that the Local Port on the Client Application and the Remote Port on the Server Application are the same.

Another text box is added to display the State property of the server. This changes from 2

(listening) to 7 (connected) as the application runs.

A final text box is added to display automatically the requestID that is sent by the client application or, optionally, to display the Local Port number for the server.

Microsoft Winsock Control 6.0 is added to manage the communications between the client and server systems. When the application runs, the server application is in a listening state. It waits for a client system to initiate a connection.

3.4 Conclusion

The first step in the development was to create a very simple Server and a very small Client on the same machine and make them communicate with no particular protocol. They were just connected one to the other:

When the Client send data to the Server, typed on the keyboard, the Server print it on the screen as soon as it is received.

The Server sends it back to the client that can read what he has sent.

It is easy to compare because the window send and receive of the Client are one under the other.

The second step was to design a fake Client able to connect to a real Server this time (DCS). The difficulty was to find a port suitable for the tests. Therefore discovering other ports available was very interesting. This version of the Client would send data to the Server that would send them back (echo port).

The following version of the Client was able to connect to any port of DCS but they couldn't communicate due to the fact that the Client did not have the protocol required. So the only way to communicate with the Server was to enter the protocol directly in a dialogue box, and it is possible to read the Server responses in a visualisation box. This method allows connecting to any port in any protocol but requires the user to know every kind of protocol and it is not user friendly for beginners. This method is then called manual method and kept in the latest version of the Client. All the TCP/IP protocols are available on the Internet and could be found quite easily because they are regrouped under a common category called RFC's, every protocol has a RFC number where the protocol is well described.

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To improve the SMTP protocol (E-mail). The Client had to send mails in an automatic way (user-friendly). The problem was different this time, the protocol was known but this was a matter of timing with the Serer. the program was too fast. So the add of a timer was necessary for a constant timing independent of the machine employed. The last problem of the SMTP protocol in automatic was the add of the return character to every line of protocol, that was a difficult bug to find and it took a lot of time to find and quite none to solve. This version is addressed to the DCS Server by default. The SMTP mode interface contains a box dedicated to the Server answers to the protocol used by the program and the user can read the Servers answers.

Previous versions contained the manual mode and the SMTP mode in automatic working well but there are some little bugs to be arranged not influent on the efficiency but on the ease to use. The automatic mode allows to send mail through the DCS Server of Napier University from any Email address (do not make any mistakes in your E-mail address) to any E-mail address on the Internet.

The versions have been improved in many ways, such as:

The addition of the FTP mode. which supports only a few commands, but sufficient to test the connection onto a real FTP server.

The addition of the Telnet mode. Which does NOT work, due to the complexity of the protocol. -The design enhancement. The windows have been covered and the objects adapted.

-The code reduction. All the test lines and useless variables, code lines have been removed.

The last contains the most important evolution on the server application; such has the multiple connection and the possibility to choose the 'listening' port. The main problem encountered is the fact that a programme can only listen to ONE port to detect if a request for connection has arrived from a client. So to test every port of a server it is needed to change the listening port. The server can handle 4 simultaneous client connection real or not, and can be very easily increased (the limit is 50-2000 depending on the type of computer). The client connected can be from all over the Internet because the uses the IP address to connect (restricted to Napier due to the Proxy). The client connected can be a real application, like FTP explorer, or the client of the package.

The possibilities of the package are:

- Up to 4 clients (real or not) connected onto the Server Application, from anywhere.

- Indicator visual and audio present to underline the present state of the connection, on both Server and Client side.

- Send plain text messages between Client and Server when the connection is established, in a test purpose.

- Perform some basic functions of an FTP client. [FTP mode]

Send E-mails through a real mail server in automatic plain text). [SMTP mode] Connect onto any server and any open port. But no protocol given. [Manual mode]

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4 Testing

4.1 Introduction

This section covers the testing of the software package. Testing is a crucial part in the successful implementations of the protocols. As the requirements have now been established, it is now crucial that a test plan be devised so that we can establish whether or not the system meets the requirements. Also if it works as expected. Portability is made easy by using Winsock Control, this guarantees true portability using industry standards. Efficiency, comes down to how fast the communications between the Client and Server perform. Reliability is mainly down to the system set-up and implementation of protocols. The TCP protocol is considered reliable. Maintainability, of the program is of the minimum as it is a straightforward Client/Server set-up and has been well documented. Usability has been addressed with an easy to follow menu system for both the Server and the Client. Functionality, have also been addressed and tested. All stages were met and satisfied.

4.2 Test Plan

1. The Telnet Test

As this part did not work, there is no test available. The main reason behind this was due to the fact that the protocol was not understood, but it did connect.

2. The SMTP Test

To test the SMTP, an email is sent through the server, using the SMTP mode. Below shows how this is achieved.

1. Select SMTP mode.

2. Type email address of the sender in the mail from box. 3. Type email address of the recipient in the mail from box. 4. Type a message in the box.

5. Choose a mail server. 6. Click on Send.

3. The HTTP Test

As this part did not completely work, there is no test available.

4. The FTP Test

The FTP can perform only very basic commands, like login, create a directory or delete it. This is the way it will work.

1. Select FTP mode. 2. Type in an IP address. 3. Select a port number. 4. Click on Connect. 5. Type in a command. 6. Click on Send.

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Problems

At first the number of object was not a problem at all. They were a few. But during the development the number of object increases and 3 solutions were possible.

Duplicate the Client application to have one form by mode, but this solution is slow to pass from one mode to the next.

Modify the size and function of each object to reduce their number and have only very few object with lots of modes and functions, but it's very complicated and the event handling would be too complicated.

Superpose the objects and use the 'visible' function to show or hide them, but it requires lots of initialisations.

The last one has been chosen because even if the code is longer, it is far simpler to build and debug.

Initialisation

This is the following problem, due to the number of objects and the need to switch from one mode to another, lots of show and hide objects is necessary. Anyway the comfort of use and the flexibility of programmatic is so much increased.

Read codes from servers

The basic functions were to send and receive data, and to connect onto a real server is one of the first steps. The thing to note is that each response of the server includes a specific code. And in those response lye two necessities, make the program understand those codes, and for the server part, create those codes. Later on, the software would only contain 2-3 of those codes, such as: 220: acknowledgements of command, ready, ok...

250: mail from ok, rcpt ok, messages sending ok...

354: start message + end of message character.

4.3 Conclusion

This chapter has illustrated the Testing side of implementing protocols. It has shown in this chapter that a lot of testing will be required. Each protocol would have to go through large amounts of testing. However as this does take up a considerable amount of time, it will only mean the protocol implementation will run successfully for a long time.

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5 Implementation

5.1 Introduction

This section details the implementation of the protocols adopted. It illustrates the User commands for TCP/IP, FTP, Telnet, SMTP.

5.2 FTP Implementation

Sending files to another computer is very important. An effective way of doing this is to use FTP.

When you open an FTP connection, you are connected to ports 20 and 21. Port 20 is the data port and port 21 is the control port. The FTP program uses TCP/IP to transfer files to and from nodes. Some commands are very similar to DOS commands, such as cd (change directory), dir (list directory), open (open node).

In FTP if you send a command such as get thisfile, the response will be:

200 PORT command successful

150 Opening ASCII mode data connection for .message 226 Transfer Complete

local: .message remote: .message

135 bytes received in 1.4 seconds (0.09 Kbytes/s)

These are some of the FTP commands:

ABOR: abort previous FTP command and any data transfer LIST filelist: list files or directories

PASS password: password on server

PORT: n1,n2,n3,n4,n5,n6: client IP address and port QUIT: logoff from server

RETR filename: get a file STOR filename: store a file SYST: server returns system type TYPE type: specify file type

USER username: username on server

In order to make FTP workable without needless error messages, the following implementation is required for all servers:

TYPE - ASCII Non-print MODE - Stream

STRUCTURE - File, Record COMMANDS - USER, QUIT, PORT, TYPE, MODE, STRU,

for the default values RETR, STOR,

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These are the default values for transfer parameters are:

TYPE - ASCII Non-print MODE - Stream

STRU - File

Here are some replies given, along with the message string:

• 125 Data connection already open; transfer starting.

• 200 Command OK

• 214 Help message

• 331 Username OK, password required

• 425 Can’t open data connection

• 452 Error writing file

• 500 Syntax error unrecognized command

• 501 Syntax error invalid arguments

• 502 Unimplemented MODE type.

FTP command generates an online reply like:

• 221 Goodbye

There are three uses for the data connection:

1. Sending a file from the client to the server. 2. Sending a file from the server to the client.

3. Sending a listing of files or directories from the server to the client.

5.3 SMTP Implementation

The email is most probably the one of the most popular applications. Commands are sent by the client to the server, and the server responds back with numerical codes. This is what happens when we send mail:

Sun % mail –v [email protected] To: [email protected]

Subject: testing

1,2,3. .

Sending letter…[email protected]…

Connecting to mailhost via ether… Trying 111.111.1.11… connected.

220 napier.ac.uk Sendmail date and time

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After the subject is entered, we then type in the message. The client does the active open to TCP port 25. It waits for a return message from the server. The server response will be the domain name. Next the client identifies itself with the HELO command. The MAIL command identifies the originator of the message and the RCPT identifies the recipient. Then by using the DATA command, the message contents are sent. The last command is QUIT, which terminates the mail exchange.

The SMTP mode was required to work in automatic, so the protocol needed to be entered by software, to be followed and dialogue with the mail server properly. Then the main requirement was to send right line of protocol, at the right time. This is where the server codes are important.

To establish a connection to a server it is necessary to follow this sequence:

- Choose the IP or DNS address of the server. - Then the port (25 for SMTP).

- And last use the 'connect' command.

Wait for a response from the server. To read that response, a filter is necessary to isolate the 3 first digits of the data received. Those digits are the response server codes.

If the code is 220 then the connection is successfully established. And it is possible to enter the

SMTP protocol:

Connection established

220

'MAIL FROM'~E-mail address

250

'RCPT TO' + E~maiI address

250

'DATA'

354

Message (plain text) +'.' on a line

250

'QUIT'

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An important point is that when a command line is sent to a server, it must be ended by two characters: line-feed (10 in ASCII) and carrier-return (13 in ASCII).

Server problems

The term server may seem very large and it is difficult to know where to start. To be simple, it is an application which 'listen' one or more ports, to detect if a Client wants to connect (request). It can handle one or multiple Client at a time. It is made in the purpose of remote connection and service.

The first step is to choose a port to listen to. Then accept only one connection, otherwise it will crash, and send a welcome message (220 + message). When it works, it is possible to make dialogues boxes to send and receive message once connected. And last, add command understood by the server, like:

- QUIT: closes the connection with the server properly.

- HELO: returns a message from the Server containing its 'P address, the 'P address of the Client performing the command and a polite 'pleased to meet you'.

Client problems

It is far more interesting if the server can accept more than one request and handle many clients simultaneously. The fact is that it is not possible to connect many clients on one socket so the best way is to open many sockets and then create some kind of mini server each one treating one client. To control this, a listening procedure that accepts, and attributes client to free sockets. The server created has been realised to handle 4 clients, but can be VERY easily expanded to a limit of 50-2000 sockets depending on the computer another limitation is the size of the form which must contain all the objects. This problem can be avoided by some kind of mode switch procedure.

A little problem was the fact the send of a last message before disconnection was necessary on the server side, because real server have one. And the difficulty is that if the close command occurs just after the send of the last message, the message seam not to be sent. Therefore a timer was necessary to close the connection about 1 sec. after the closing message.

5.4 TCP Implementation

TCP is a connection-oriented, reliable transport protocol. A connection-oriented protocol implies that the two hosts participating in a discussion must first establish a connection before data may be exchanged. In TCP’s case, this is done with the three-way handshake. Reliability can be provided in a number of ways, like data sequencing and acknowledgement. TCP assigns sequence numbers to every byte in every segment and acknowledges all data bytes received from the other end.

In order to exchange data using TCP, hosts must establish a connection. TCP establishes a connection in a 3-step process called the 3-way handshake. If machine A is running a Client program and wishes to connect to a Server program on machine B, the process is as follows:

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a. A sends SYN to B

b. A receives SYN/ACK from B c. A sends ACK to B

At a., the Client is telling the server that it wants a connection. This is the SYN flag’s only purpose. The Client is telling the Server that the sequence number field is valid, and should be checked. The Client will set the sequence number field in the TCP header to its ISN (initial sequence number). The Server, upon receiving this segment. will respond with its own ISN ( therefore the SYN flag is on) and an Acknowledgement of the Client’s first segment (which is the Client’s ISN+1). The Client then Acknowledges the Server’s ISN c. Now data transfer may take place.

5.6 Conclusion

This chapter has demonstrated how you can use Telnet, SMTP and FTP to connect to and use several other TCP/IP services. Implementation of any given protocol must comply to the rules set out in RFC documents. These documents are the origination of the protocols and provide many useful insights into any given protocol.

Within these RFC documents are many User commands which prove to be very helpful. They describe the history of these protocols. As the Internet is always growing its hard to tell what future will hold for the various protocols.

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6 6

Conclusion

As the software stands, HTTP and other protocols were not implemented to success due to the time factor. At this stage, the manual connection to any port of any Server is working, so is the SMTP protocol in automatic, with no restriction concerning the servers. The FTP mode is, concerning the project requirement, achieved, but can be improved if it is needed. Unfortunately, the Telnet is not really a success, it only connects, but the Telnet protocol needs a lot of parameters and exchanges between the client and the server, and the code appears to be in 7-bit ASCII instead of the 8-bit windows ASCII. To improve this last mode, a lot of changes are necessary and the code largely complicated.

The Client software was the first part of the project and was a bit late in the timescale. The Server side was very hard to start but a lot of researched over the web and on line tutorials were very useful. The difficulty was that the solutions provided were created to fit Visual Basic 6, version more recent than Napier's one. But the structure, quite complex, was understandable, and successfully implemented into the project's code.

The Server is, for me, was a success, as well as the Client which the possibilities are easily extendable, and would suit a slightly different subject. The Server is complete about the connection, but can be upgraded not only on the number of Client connected, but also on the treatment of the information. It can be dedicated to one port and become only an FTP Server, or anything else, by adding the corresponding code.

This project was very interesting. I didn't know Visual Basic at all when I started this project. It was a good experience learning it. It is a very useful development tool, especially for socket programming. The software can be upgraded in future, to include the implementation of further protocols.

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Appendix 1 Documentation and Screen Shots

The software will run on any Windows PC. You will not have to install Visual Basic 6.

The program is called TCP/IP Emulator. By clicking the program you will see an option screen for a Client or a Server program. By clicking on the protocol buttons will allow you access to the TCP/IP protocols.

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Appendix 2 RFC’s

All the required commands, rules and order of entering commands you can find in RFC (request for comments) documents.

Protocol RFC Link

SMTP 821 http://www.faqs.org/rfcs/rfc821.html POP3 1725 http://www.faqs.org/rfcs/1725.html HTTP 2068 http://www.faqs.org/rfcs/rfc2068.html FTP 959 http://www.faqs.org/rfcs/rfc959.html

Above are just a few of the thousands of RFCs available. The set of commands and responses is unique for every protocol.

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Appendix 3 Source Code

Client Code

'Last modification: 20/04/2001 FTP & SMTP & Manual mode only

Dim Mode As String

Dim ProtocolSMTP As Integer Dim CounterOk As Integer Dim LoopCount As Long Dim Temps As Long

Dim ModeSMTP As Integer

Private Sub Form_Load()

Unload ChoiceSC 'Close the main menu properly SendTextData.Enabled = False 'Initialisation SendTextDatalbl.Enabled = False

cmdDisConnect.Visible = False cmdConnect.Visible = True AddressIP.Enabled = True AddressPort.Enabled = False

PortNameC.Visible = False 'Init manual mode AddressPort.Visible = False AddressIP.Visible = False PortNameClbl.Visible = False AddressPortlbl.Visible = False AddressIPlbl.Visible = False cmdConnect.Visible = False cmdDisConnect.Visible = False SendData.Visible = False SendTextData.Visible = False ShowText.Visible = False SendTextDatalbl.Visible = False ShowTextlbl.Visible = False ConnectionStateM.Visible = False ConnectionStateMlbl.Visible = False red.Visible = False green.Visible = False Radiation.Visible = False

MailFrom.Visible = False 'Init SMTP mode MailTo.Visible = False Message.Visible = False MailFromlbl.Visible = False MailTolbl.Visible = False Messagelbl.Visible = False ServerAnswer.Visible = False

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ServerAnswerlbl.Visible = False ResetSMTP.Visible = False

FtpServerAnswer.Visible = False 'Init FTP mode FtpCommand.Visible = False FtpCommandlbl.Visible = False FtpServerChoice.Visible = False FtpServerChoicelbl.Visible = False FtpPortChoice.Visible = False FtpPortChoicelbl.Visible = False ResetFTPTelnet.Visible = False SendData.Caption = "Send" FtpTelnetSend.Visible = False

TelnetServerAnswer.Visible = False 'Init TELNET mode TelnetCommand.Visible = False TelnetCommandlbl.Visible = False TelnetServerChoice.Visible = False TelnetServerChoicelbl.Visible = False TelnetPortChoice.Visible = False TelnetPortChoicelbl.Visible = False ResetFTPTelnet.Visible = False SendData.Caption = "Send" FtpTelnetSend.Visible = False

CounterOk = 0 'Init variables ModeSMTP = 0

End Sub

Private Sub Ftp_Click() Mode = "FTP"

FtpServerAnswer.Text = ""

TelnetServerAnswer.Visible = False 'Disable TELNET mode TelnetCommand.Visible = False TelnetCommandlbl.Visible = False TelnetServerChoice.Visible = False TelnetServerChoicelbl.Visible = False TelnetPortChoice.Visible = False TelnetPortChoicelbl.Visible = False ResetFTPTelnet.Visible = False SendData.Caption = "Send" FtpTelnetSend.Visible = False

FtpServerAnswer.Visible = True 'Enable FTP mode FtpCommand.Visible = True FtpCommandlbl.Visible = True FtpServerChoice.Visible = True FtpServerChoicelbl.Visible = True FtpPortChoice.Visible = True FtpPortChoicelbl.Visible = True ResetFTPTelnet.Visible = False SendData.Caption = "Connect" FtpTelnetSend.Visible = False

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red.Visible = True green.Visible = False Radiation.Visible = False

PortNameC.Visible = False 'Disable manual mode objects AddressPort.Visible = False AddressIP.Visible = False PortNameClbl.Visible = False AddressPortlbl.Visible = False AddressIPlbl.Visible = False cmdConnect.Visible = False cmdDisConnect.Visible = False SendData.Visible = True SendTextData.Visible = False ShowText.Visible = False SendTextDatalbl.Visible = False ShowTextlbl.Visible = False ConnectionStateM.Visible = False ConnectionStateMlbl.Visible = False

MailFrom.Visible = False 'Disable SMTP mode ojects MailTo.Visible = False Message.Visible = False MailFromlbl.Visible = False MailTolbl.Visible = False Messagelbl.Visible = False ServerAnswer.Visible = False ServerAnswerlbl.Visible = False ResetSMTP.Visible = False End Sub

Private Sub Manuel_Click() Mode = "Manual"

SendTextData.Text = ""

PortNameC.Visible = True 'Init Manual mode objects AddressPort.Visible = True AddressIP.Visible = True PortNameClbl.Visible = True AddressPortlbl.Visible = True AddressIPlbl.Visible = True cmdConnect.Visible = True cmdDisConnect.Visible = False SendData.Visible = False SendTextData.Visible = True ShowText.Visible = True SendTextDatalbl.Visible = True ShowTextlbl.Visible = True ConnectionStateM.Visible = True ConnectionStateMlbl.Visible = True ConnectionStateM.Text = "Disconnected"

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red.Visible = True green.Visible = False Radiation.Visible = False

MailFrom.Visible = False 'Disable SMTP mode ojects MailTo.Visible = False Message.Visible = False MailFromlbl.Visible = False MailTolbl.Visible = False Messagelbl.Visible = False ServerAnswer.Visible = False ServerAnswerlbl.Visible = False ServerAnswer.Visible = False ServerAnswerlbl.Visible = False ResetSMTP.Visible = False

FtpServerAnswer.Visible = False 'Disable FTP mode FtpCommand.Visible = False FtpCommandlbl.Visible = False FtpServerChoice.Visible = False FtpServerChoicelbl.Visible = False FtpPortChoice.Visible = False FtpPortChoicelbl.Visible = False ResetFTPTelnet.Visible = False SendData.Caption = "Send" FtpTelnetSend.Visible = False

TelnetServerAnswer.Visible = False 'Disable TELNET mode TelnetCommand.Visible = False TelnetCommandlbl.Visible = False TelnetServerChoice.Visible = False TelnetServerChoicelbl.Visible = False TelnetPortChoice.Visible = False TelnetPortChoicelbl.Visible = False ResetFTPTelnet.Visible = False SendData.Caption = "Send" FtpTelnetSend.Visible = False End Sub

Private Sub Smtp_Click() Mode = "SMTP"

PortNameC.Visible = False 'Disable manual mode objects AddressPort.Visible = False AddressIP.Visible = False PortNameClbl.Visible = False AddressPortlbl.Visible = False AddressIPlbl.Visible = False cmdConnect.Visible = False cmdDisConnect.Visible = False SendData.Visible = True SendTextData.Visible = False ShowText.Visible = False SendTextDatalbl.Visible = False

DIAGNOSTIC TOOL FOR HIGHER LEVEL PROTOCOL TESTING ON A TCP/IP BASED NETWORK FAISAL ASLAM