Example of proxy TCP echo server. Useful for debugging and analysing incoming traffic.

proxy_tcp_server.py

# Proxy echo TCP server program
import socket


HOST = "localhost"
PORT = 6667
HOST_NEW = "localhost"
PORT_NEW = 6666
CONNECTED = False

s = socket.socket()
s.bind((HOST, PORT))
s.listen(5)

print("\n--------------\nStart listening")
conn, addr = s.accept()
with conn:
    while True:
        data = conn.recv(4096)
        print(f"-------------\nFROM CLIENT:\n{data}\n-------------\n")

        if not CONNECTED:
            s2 = socket.socket()
            s2.connect((HOST_NEW, PORT_NEW))
            CONNECTED = True
        s2.sendall(data)

        data = s2.recv(4096)
        print(
            f"------------------\nFROM SERVER:\n{data!r}\n------------------\n"
        )

        print(r"##################")
        conn.send(data)