tcp_example.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# A simple fibonacci number server using TCP/IP, 
# which can handle multiple clients.
from __future__ import print_function
from socket import *
import argparse
import os, sys

cache = {0: 1, 1:1}
MAX_BYTES = 1024
MAX_NUM_CLIENTS = 10

def fibo(n):
    if n in cache:
        return cache[n]
    else:
        cache[n] = fibo(n-1) + fibo(n-2)
        return cache[n]

def server(ip, port):
    sock = socket(AF_INET, SOCK_STREAM)
    sock.bind((ip, port))
    print("Fibonacci Server version 1.0")
    print("Listening at {}:{}".format(*sock.getsockname()))

    greeting = "Welcome to fibonacci server using TCP/IP..."
    sock.listen(MAX_NUM_CLIENTS)
    clients = []
    while True:
        client, address = sock.accept()
        # I need a fork here.....
        newPID = os.fork()
        if newPID == 0:
            client.send(greeting)
            while True:
                print("child", os.getpid())
                data = client.recv(20)
                if data != "":
                    print("Client sending: {}".format(data))
                    try:
                        n = int(data)
                    except ValueError:
                        client.send("Invalid data...")
                        continue
                    result = fibo(n)
                    client.send(str(result))
                else:
                    client.send("Closing connection....")
                    client.close()
                    sys.exit(0)
        else:
            clients.append(address)
            print("Connected clients: {}".format(clients))


def client(ip, port):
    sock = socket(AF_INET, SOCK_STREAM)
    print("Connecting to {}:{}....".format(ip, port))
    sock.connect((ip, port))
    msg = sock.recv(1000)
    print(msg)

    while True:
        n = raw_input("Enter an integer: ")

        if n == "":
            print("Closing socket....")
            sock.close()
            break

        sock.send(n)
        result = sock.recv(MAX_BYTES)
        print("Recieving from server: {}".format(result))

if __name__ == "__main__":
    choices = {"client": client, "server": server}
    parser = argparse.ArgumentParser()
    parser.add_argument("role", choices = choices)
    parser.add_argument("-p", "--port", type = int, dest = "p")
    args = parser.parse_args()
    function = choices[args.role]
    function("127.0.0.1", args.p)