Aaaaannd here is another post of mine on sockets, client/server models and stuff. I suppose you have started to get bored by the same stuff everyday right? Seems like I just can't get enough of this thing. But trust me, I had no intention of doing this today, a friend of mine instigated me write a messenger for a project we were working on, and it turned out, writing this simple messaging program was more interesting than I thought.

So, instead of creating a straight forward chat program that was 'actually' required by my friend, I created this 'one-server-multiple-clients' program, which is more like the real world chat apps we use everyday.

To run the program, execute the 'server.py' (after changing the bind() address to the address of the server on which it is supposed to run). Then, execute the 'client.py' (guess what? same thing here. But you will have to add the server address in the connect() function here). Of course, you can have all of them running on the same system, but there ain't any fun in it, right?

Last but not the least, I have commented as much as I could, unlike my last article, so I expect everyone reading this, with a bit of programming knowledge, will understand this straight forward code.

server.py

# Import the necessary libraries
import socket
import sys
import select
# Take message from an host and send it to all others
def shout(sock, message):
  for socket in LIST:
    try:
      # Don't send it back to server and yourself!
      if socket != serv and socket != sock:
        socket.send(message)
    except:
      # Assume client has got disconnected and remove it.
      socket.close
      LIST.remove(socket)
# Declare variables required later.
# To store list of sockets of clients as well as server itself.
LIST = []
# Common buffer for all purposes
buff = 1024
# Declaration of Server socket.
serv = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
serv.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
serv.bind(("192.168.1.10", 1356))
# Listen for upto 6 clients. Increase if you need more.
serv.listen(6)
# Add server socket to the LIST
LIST.append(serv)
while 1:
  # Moniter clients all simultaneously
  reads, writes, err = select.select(LIST, [], [])
  for sock in reads:
    # A new client connected?
    if sock == serv:
      sockfd, addr = serv.accept()
      LIST.append(sockfd)
    # Naah, just a new message!
    else:
      try:
        # Get his shitty message.
        data = sock.recv(buff)
        if data:
          # If he wrote something, send it to shout() function for broadcast.
          shout(sock, data)
      ;except:
        # Shit just got real. Client kicked by server :3
        sock.close()
        LIST.remove(sock)
        # Do this till the end of time.
        continue
serv.close()

client.py 

# Import the nessary libraries
import socket
import string
import select
import sys

# Socket variable declaration
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.settimeout(2)

# Connect to server. Change this for remote servers.
s.connect(("192.168.1.10", 1356))

# A prompt asking client to enter something.
sys.stdout.write(">")
sys.stdout.flush()

while 1:
  # These are the possible events.
  # sys.stdin --> Client has typed something through keyboard.
  # s --> Server has send a new message by some other client you.
  streams = [sys.stdin, s]

  # Moniter both the streams simultaneously for inputs.
  readable, writable, err = select.select(streams, [], [])

  # If server has sent something, readable will fill up.
  for sock in readable:
    if sock == s:

      # Receive data in our variable. Check if it is empty.
      data = sock.recv(1024)
      if not data:
        sys.exit()
      else:

        # Write data to stdout and give client prompt back.
        sys.stdout.write(data)
        sys.stdout.write(">")
        sys.stdout.flush()

    # No, its not the server. Our client has typed something in.
    else:

      # Read message. Send it to server. Give prompt back to client.
      msg = sys.stdin.readline()
      s.send(msg)
      sys.stdout.write(">")
      sys.stdout.flush()

So that was the code. Here is a glimpse of the output. The server is running off my 'raspberrypi' and all clients are running on my computer. Looks cool right?

If you look closely, one of the clients missed a message sent by another client, LOL, so that is normal. Any suggestions or edits or corrections, drop them in the comments below. :)