How to Implement Simple Mail Transfer Protocol in OMNeT++

To Implement the Simple Mail Transfer Protocol (SMTP) in OMNeT++ has generate the emulation design wherever an SMTP client commonly a mail user agent, MUA that interacts communicates with an SMTP server  that frequently in a mail transfer agent, MTA over a network. This execution needs to describe essential modules for the SMTP client and server, manage the connection establishment, sending email messages, and closing the connection. The given below are the detailed procedures on how to implement the SMTP in OMNeT++:

Step-by-Step Implementation:

Step 1: Set Up the OMNeT++ Environment

1. Install OMNeT++:
   • Make certain that OMNeT++ is installed on system. We need to download it from the official OMNeT++
2. Install the INET Framework:
   • The INET Framework is required for network simulations as it offers models for basic network protocols such as TCP/IP, which SMTP relies on.
   • Download and install INET from the INET Framework GitHub repository.

Step 2: Create a New OMNeT++ Project

1. Create the Project:
   • Open OMNeT++ and generates a new OMNeT++ project through File > New > OMNeT++ Project.
   • Name project like SMTP_Simulation and set up the project directory.
2. Set Up Project Dependencies:
   • Guarantee project references the INET Framework by right-clicking on project in the Project Explorer, navigating to Properties > Project References, and checking the INET project.

Step 3: Understand SMTP Basics

Before proceeding with the implementation, understand yourself with the core concepts of SMTP:

• SMTP Client (MUA): The client that sends emails.
• SMTP Server (MTA): The server that receives emails from clients and forwards them to the destination server.
• SMTP Commands: Commands like HELO, MAIL FROM, RCPT TO, DATA, QUIT, etc.
• SMTP Response Codes: Standard response codes like 250 (OK), 354 (Start mail input), and 550 (Requested action not taken).

Step 4: Define the Network Topology in OMNeT++

1. Create a NED File:
   • Describe the network topology using the NED language. The topology should contain an SMTP client, SMTP server, and potentially a network infrastructure like routers.

Example:

network SMTPNetwork

{

submodules:

client: StandardHost;

server: StandardHost;

router: Router;

connections:

client.ethg++ <–> Eth10Mbps <–> router.ethg++;

server.ethg++ <–> Eth10Mbps <–> router.ethg++;

}

1. Configure Network Parameters:
   • Set up network parameters such as bandwidth, delay, and packet loss.

Step 5: Implement SMTP Protocol

1. Define SMTP Modules:
   • Make NED modules for the SMTP client and server. These modules will manage the simple SMTP operations like connection setup, sending commands, and receiving responses.

Example (in NED):

simple SMTPClient

{

parameters:

@display(“i=block/cogwheel”);

gates:

inout tcpIn;

inout tcpOut;

}

simple SMTPServer

{

parameters:

@display(“i=block/cogwheel”);

gates:

inout tcpIn;

inout tcpOut;

}

1. Implement SMTP Logic in C++:
   • SMTP Client Implementation:
     • Write the C++ code for the SMTP client module. The client should inaugurate a TCP connection with the SMTP server, send SMTP commands, and manage server responses.

Example (in C++):

void SMTPClient::handleMessage(cMessage *msg) {

if (msg->isSelfMessage()) {

initiateConnection();

} else if (msg->arrivedOn(“tcpIn”)) {

handleServerResponse(msg);

}

}

void SMTPClient::initiateConnection() {

TCPSocket *socket = new TCPSocket();

socket->setCallbackObject(this, nullptr);

socket->connect(IPAddressResolver().resolve(“server”), 25);  // Port 25 for SMTP

}

void SMTPClient::handleServerResponse(cMessage *msg) {

TCPSegment *tcpSegment = check_and_cast<TCPSegment *>(msg);

if (tcpSegment->getPayload()) {

std::string response = tcpSegment->getPayload()->str();

// Process server’s response and send the next command

if (response.find(“220”) != std::string::npos) {

// Send HELO command

} else if (response.find(“250”) != std::string::npos) {

// Handle MAIL FROM, RCPT TO, etc.

}

}

}

1. • SMTP Server Implementation:
     • To execute the SMTP server module. The server should listen for incoming TCP connections, process SMTP commands, and send appropriate responses.

Example (in C++):

void SMTPServer::handleMessage(cMessage *msg) {

if (msg->arrivedOn(“tcpIn”)) {

handleClientRequest(msg);

}

}

 

void SMTPServer::handleClientRequest(cMessage *msg) {

TCPSegment *tcpSegment = check_and_cast<TCPSegment *>(msg);

std::string request = tcpSegment->getPayload()->str();

if (request.find(“HELO”) != std::string::npos) {

sendResponse(250, “OK”);

} else if (request.find(“MAIL FROM”) != std::string::npos) {

// Process MAIL FROM and send a response

} else if (request.find(“RCPT TO”) != std::string::npos) {

// Process RCPT TO and send a response

} else if (request.find(“DATA”) != std::string::npos) {

// Handle the message data

sendResponse(354, “Start mail input”);

}

}

void SMTPServer::sendResponse(int code, const std::string &message) {

std::ostringstream response;

response << code << ” ” << message;

TCPSegment *responseSegment = new TCPSegment();

responseSegment->setPayload(makeShared<ByteArrayChunk>(response.str()));

send(responseSegment, “tcpOut”);

}

1. Create SMTP Message Types:
   • Define custom message types for SMTP commands and responses.

Example (in C++):

class SMTPMessage : public cMessage {

public:

std::string command;

std::string argument;

…

};

Step 6: Configure the Simulation

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

Example:

network = SMTPNetwork

*.client.numTcpApps = 1

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

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

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

*.client.tcpApp[0].connectPort = 25

*.server.numTcpApps = 1

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

*.server.tcpApp[0].localPort = 25

1. Define SMTP Scenarios:
   • Specify the SMTP scenarios to simulate, like sending a simple email message or mimic the multiple concurrent SMTP sessions.

Step 7: Simulate and Test SMTP

1. Compile the Project:
   • Build OMNeT++ project to make sure everything is implemented properly.
2. Run the Simulation:
   • Implement the simulation and monitor how the SMTP client and server interact. Make certain that the client can effectively send email messages to the server.
3. Analyse Results:
   • Use OMNeT++ tools to monitor SMTP messages, response times, and overall protocol performance. Validate that SMTP implementation works appropriately under altered network conditions.

Step 8: Refine and Extend

1. Enhance SMTP Functionality:
   • Add more advanced topographies to SMTP implementation has handling email attachments, supporting multiple recipients, or applying the error handling and retry mechanisms.
2. Test with Different Network Configurations:
   • Run simulations under several network conditions such as high latency, packet loss to verify the robustness of SMTP implementation.
3. Performance Optimization:
   • Enhance the implementation to manage multiple concurrent connections efficiently and diminish overhead.

Overall, we had discussed more information regarding the Simple Mail Transfer Protocol that has generate the simulation model and then the SMTP client communicate with the server with the help of OMNeT++ tool. Additional information will provide in the further setup in different simulation tool.

If you need help with implementing Simple Mail Transfer Protocol in OMNeT++, our developers can provide you with project topics and steps to execute. Just send us your project details, and we’ll help you out with your project performance!