import socket
import threading
import time


# Simple TCP server that listens and accepts a connection.
def server():
    srv = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    srv.bind(("127.0.0.1", 12345))
    srv.listen(5)
    print("Server: Listening on port 12345...")
    # This accept() call is where the kernel's inet_csk_accept() is invoked.
    conn, addr = srv.accept()
    print(f"Server: Accepted connection from {addr}")
    conn.sendall(b"Hello, client!")
    conn.close()
    srv.close()


# Simple TCP client that connects to the server.
def client():
    time.sleep(1)  # Give the server a moment to start listening.
    cli = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    cli.connect(("127.0.0.1", 12345))
    data = cli.recv(1024)
    print("Client: Received:", data.decode())
    cli.close()


if __name__ == "__main__":
    # Start server and client in separate threads.
    server_thread = threading.Thread(target=server)
    client_thread = threading.Thread(target=client)

    server_thread.start()
    client_thread.start()

    server_thread.join()
    client_thread.join()
   
# eBPF based program will catch the following program's socket event like below.
# {"eventname":"tcpV4Accept","source":"eBPF","timestamp":"2025-03-21T14:09:59.506519+09:00","log":"A TCP connection has been accepted","metadata":{"LocalIP":"127.0.0.1","LocalPort":14640,"PID":117642,"RemoteIP":"127.0.0.1","RemotePort":54996,"UID":1000}