How to Implement File Transfer Protocol in OMNeT++

To implement the File Transfer Protocol (FTP) in OMNeT++ encompasses to making a simulation model where an FTP client communicates with an FTP server over a network. The implementation needs to describing FTP-specific messages, managing the connection establishment, closing the connection, and data transfer.

The following is a step-by-step procedure to implement FTP in OMNeT++:

Step-by-Step Implementations:

Step 1: Set Up the OMNeT++ Environment

1. Install OMNeT++:
   • Make sure OMNeT++ is installed on the system.
2. Install the INET Framework:
   • To download and install the INET Framework, which offers essential network models and protocols like TCP/IP, which FTP relies on.
   • The INET Framework can be downloaded from its GitHub repository.

Step 2: Create a New OMNeT++ Project

1. Create the Project:
   • Open OMNeT++ and make a new project by choosing File > New > OMNeT++ Project.
   • Name the project, for example, FTP_Simulation, and set up the project directory.
2. Set Up Project Dependencies:
   • Make sure the project references the INET Framework. Right-click on the project in the Project Explorer, go to Properties > Project References, and verify the INET project.

Step 3: Define the Network Topology in OMNeT++

1. Create a NED File:
   • Use the NED language to define the network topology, which contains an FTP client, an FTP server, and the network like routers, switches connecting them.

Example:

network FTPNetwork

{

submodules:

client: StandardHost;

server: StandardHost;

router: Router;

connections:

client.pppg++ <–> PointToPointLink <–> router.pppg++;

server.pppg++ <–> PointToPointLink <–> router.pppg++;

}

1. Configure Network Parameters:
   • State link parameters like bandwidth and delay in the network configuration.

Step 4: Implement FTP Protocol

1. Define FTP Modules:
   • To make NED modules for the FTP client and server. These modules will manage the FTP-specific operations like connection establishment, file transfer, and interruption.

Example (in NED):

simple FTPClient

{

parameters:

@display(“i=block/cogwheel”);

gates:

inout tcpIn;

inout tcpOut;

}

simple FTPServer

{

parameters:

@display(“i=block/cogwheel”);

gates:

inout tcpIn;

inout tcpOut;

}

1. Implement FTP Logic in C++:
   • FTP Client Implementation:
     • Mark the C++ code for the FTP client module. The client should initiate a TCP connection to the FTP server, send instructions to request files, and manage the incoming data.

Example (in C++):

void FTPClient::handleMessage(cMessage *msg) {

// Handle TCP connection establishment

if (msg->isSelfMessage()) {

connectToServer();

} else if (msg->arrivedOn(“tcpIn”)) {

handleServerResponse(msg);

}

}

void FTPClient::connectToServer() {

// Send a TCP connect request

TCPSocket *socket = new TCPSocket();

socket->setCallbackObject(this, nullptr);

socket->connect(IPAddressResolver().resolve(“server”), 21);

}

void FTPClient::handleServerResponse(cMessage *msg) {

// Process the data from the server

if (/* server sends data */) {

// Handle file data

}

}

1. • FTP Server Implementation:
     • To implement the FTP server module to listen for incoming TCP connections, respond to FTP commands, and send requested files.

Example (in C++):

void FTPServer::handleMessage(cMessage *msg) {

if (msg->arrivedOn(“tcpIn”)) {

handleClientRequest(msg);

}

}

void FTPServer::handleClientRequest(cMessage *msg) {

// Process FTP commands and send appropriate responses

if (/* client requests a file */) {

sendFileData();

}

}

void FTPServer::sendFileData() {

// Send the file data to the client

// This can be done by splitting the file into chunks and sending them over the TCP connection

}

1. Create FTP Message Types:
   • Generate custom message types for FTP commands and responses like STOR, RETR, LIST, etc.

Example (in C++):

class FTPCommand : public cMessage {

public:

std::string command;

std::string argument;

…

};

class FTPData : public cMessage {

public:

std::string fileName;

std::vector<uint8_t> dataChunk;

…

};

Step 5: Configure the Simulation

1. Set Up the TCP/IP Stack:
   • In the omnetpp.ini file, configure the FTP client and server to custom the TCP/IP stack given by the INET Framework.

Example:

[General]

network = FTPNetwork

*.client.numTcpApps = 1

*.client.tcpApp[0].typename = “TCPGenericCliApp”

*.client.tcpApp[0].localPort = -1

*.client.tcpApp[0].connectAddress = “server”

*.client.tcpApp[0].connectPort = 21

*.server.numTcpApps = 1

*.server.tcpApp[0].typename = “TCPGenericSrvApp”

*.server.tcpApp[0].localPort = 21

1. Define FTP Scenarios:
   • Identify the FTP scenarios to mimic, like file upload/download, and the size of files to be transferred.

Step 6: Simulate and Test FTP

1. Compile the Project:
   • Build the project in OMNeT++ to make sure everything is properly implemented.
2. Run the Simulation:
   • Perform the simulation and observe how the FTP client and server interact. Verify if the client can successfully retrieve files from the server.
3. Analyse Results:
   • Use OMNeT++ tools to display the throughput, delay, and reliability of file transfers. Check that the FTP implementation works correctly under several network conditions.

Step 7: Refine and Extend

1. Enhance FTP Functionality:
   • Increase more advanced features to the FTP implementation, like passive mode, error handling, or multi-file transfer support.
2. Test with Different Network Configurations:
   • Run simulations under several network conditions like high latency, packet loss to test the robustness of the FTP implementation.
3. Performance Optimization:
   • Enhance the implementation to handle big files efficiently, minimalize overhead, and make sure scalability.

More detailed information is discussed about to implement File Transfer Protocol using the tool OMNeT++ in this paper. We will provide additional implementation and project execution details about to execute File Transfer Protocol in other tools.