solo.py

#!/usr/bin/env python
# inspired by http://timkay.com/solo/

import socket
import sys
import subprocess

HOST=''
port = int(sys.argv[1])

sock = None

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

try:
    sock.bind((HOST,port))
except socket.error:
    print("locked!")
    sock.close()
    sys.exit(0)
    
subprocess.call(sys.argv[2:])