sctptest.py

#!/usr/bin/env python3

"""
SCTP Client/Server
Author: Fahad Yousuf

This script implements a simple SCTP client/server using Python's socket module.
The server listens on port 62324 and the client connects to the server on the same port.
"""

import socket
import sys
import os
import argparse
from datetime import datetime

PORT = 62324
DEFAULT_SERVER_ADDR = '127.0.0.1'

def output(message):
    timestamp = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
    print(f"{timestamp} - {message}")


def get_local_ip(remote_addr):
    """Retrieve local IP address used for connection to remote server."""
    try:
        # Create a temporary socket to determine local IP
        temp_sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
        temp_sock.connect((remote_addr, 80))
        local_ip = temp_sock.getsockname()[0]
        temp_sock.close()
        return local_ip
    except Exception as e:
        output(f"Error getting local IP: {e}")
        return '127.0.0.1'

def server(port=PORT):
    """SCTP Server implementation."""
    try:
        # Create SCTP socket
        server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM, socket.IPPROTO_SCTP)
        
        # Bind to all interfaces
        server_socket.bind(('0.0.0.0', port))
        server_socket.listen(5)
        
        output(f"Server listening on port {port}")
        
        while True:
            # Accept incoming connection
            client_socket, addr = server_socket.accept()
            output(f"Connection from {addr}")
            
            # Receive message
            data = client_socket.recv(1024).decode()
            output(f"Received: {data}")
            
            client_socket.close()
    
    except Exception as e:
        output(f"Server error: {e}")
        sys.exit(1)

def client(server_addr, port=PORT):
    """SCTP Client implementation."""
    try:
        # Get local IP
        local_ip = get_local_ip(server_addr)
        
        # Create SCTP socket
        client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM, socket.IPPROTO_SCTP)
        
        # Connect to server
        client_socket.connect((server_addr, port))
        
        # Prepare message with local IP
        message = f"Hello Server, from {local_ip}"
        
        # Send message
        client_socket.send(message.encode())
        output(f"Sent message: {message}")
        
        client_socket.close()
    
    except Exception as e:
        output(f"Client error: {e}")
        sys.exit(1)

def main():
    # Parse command-line arguments
    parser = argparse.ArgumentParser(description='SCTP Client/Server')
    parser.add_argument('-m', '--mode', type=str, choices=['server', 'client'], 
                        help='Select server or client mode', default='client')
    parser.add_argument('-s','--server_addr', type=str, default=DEFAULT_SERVER_ADDR, 
                        help='Server address to connect to')
    parser.add_argument('-p', '--port', type=int, default=PORT, 
                        help='Port to connect to or listen on')
    args = parser.parse_args()

    if args.mode == "server":
        mode = "server"
    else:
        mode = "client"
        
    if mode == "server":
        server(port=args.port)
    elif mode == "client":
        output("Running in client mode")
        client(args.server_addr, args.port)
    else:
        output("Select server or client mode")
        sys.exit(1)

if __name__ == '__main__':
    main()