Python Networking

Remarks

(Very) basic Python client socket example

Creating a Simple Http Server

To share files or to host simple websites(http and javascript) in your local network, you can use Python's builtin SimpleHTTPServer module. Python should be in your Path variable. Go to the folder where your files are and type:

For python 2:

$ python -m SimpleHTTPServer <portnumber>

For python 3:

$ python3 -m http.server <portnumber>

If port number is not given 8000 is the default port. So the output will be:

Serving HTTP on 0.0.0.0 port 8000 ...

You can access to your files through any device connected to the local network by typing http://hostipaddress:8000/.

hostipaddress is your local ip address which probably starts with 192.168.x.x.

To finish the module simply press ctrl+c.

Creating a TCP server

You can create a TCP server using the socketserver library. Here's a simple echo server.

Server side

from sockerserver import BaseRequestHandler, TCPServer

class EchoHandler(BaseRequestHandler):
    def handle(self):
        print('connection from:', self.client_address)
        while True:
            msg = self.request.recv(8192)
            if not msg:
                break
            self.request.send(msg)

if __name__ == '__main__':
    server = TCPServer(('', 5000), EchoHandler)
    server.serve_forever()

Client side

from socket import socket, AF_INET, SOCK_STREAM
sock = socket(AF_INET, SOCK_STREAM)
sock.connect(('localhost', 5000))
sock.send(b'Monty Python')
sock.recv(8192)  # returns b'Monty Python'

socketserver makes it relatively easy to create simple TCP servers. However, you should be aware that, by default, the servers are single threaded and can only serve one client at a time. If you want to handle multiple clients, either instantiate a ThreadingTCPServer instead.

from socketserver import ThreadingTCPServer
...
if __name__ == '__main__':
    server = ThreadingTCPServer(('', 5000), EchoHandler)
    server.serve_forever()

Creating a UDP Server

A UDP server is easily created using the socketserver library.

a simple time server:

import time
from socketserver import BaseRequestHandler, UDPServer

class CtimeHandler(BaseRequestHandler):
    def handle(self):
    print('connection from: ', self.client_address)
    # Get message and client socket
    msg, sock = self.request
    resp = time.ctime()
    sock.sendto(resp.encode('ascii'), self.client_address)

if __name__ == '__main__':
    server = UDPServer(('', 5000), CtimeHandler)
    server.serve_forever()

Testing:

>>> from socket import socket, AF_INET, SOCK_DGRAM
>>> sock = socket(AF_INET, SOCK_DGRAM)
>>> sick.sendto(b'', ('localhost', 5000))
0
>>> sock.recvfrom(8192)
(b'Wed Aug 15 20:35:08 2012', ('127.0.0.1', 5000))

Start Simple HttpServer in a thread and open the browser

Useful if your program is outputting web pages along the way.

from http.server import HTTPServer, CGIHTTPRequestHandler
import webbrowser
import threading

def start_server(path, port=8000):
    '''Start a simple webserver serving path on port'''
    os.chdir(path)
    httpd = HTTPServer(('', port), CGIHTTPRequestHandler)
    httpd.serve_forever()

# Start the server in a new thread
port = 8000
daemon = threading.Thread(name='daemon_server',
                          target=start_server,
                          args=('.', port)
daemon.setDaemon(True) # Set as a daemon so it will be killed once the main thread is dead.
daemon.start()

# Open the web browser 
webbrowser.open('http://localhost:{}'.format(port))

The simplest Python socket client-server example

Server side:

import socket

serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
serversocket.bind(('localhost', 8089))
serversocket.listen(5) # become a server socket, maximum 5 connections

while True:
    connection, address = serversocket.accept()
    buf = connection.recv(64)
    if len(buf) > 0:
        print(buf)
    break

Client Side:

import socket

clientsocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
clientsocket.connect(('localhost', 8089))
clientsocket.send('hello')

First run the SocketServer.py, and make sure the server is ready to listen/receive sth Then the client send info to the server; After the server received sth, it terminates