Referring to previous post, we will continue with same code. In this post we will try to handle multiple clients.
Multiple clients means that multiple client programs can connect to server program. For this we will use threads. Threads are nothing but process and runs only the part that is required (we decide what is going to run) to be run.
There will be a minor change in both server and client programs.
Required: Python 2.6+
#!/usr/bin/python # Import all from module socket from socket import * #Importing all from thread from thread import * # Defining server address and port host = '' #'localhost' or '127.0.0.1' or '' are all same port = 52000 #Use port > 1024, below it all are reserved #Creating socket object sock = socket() #Binding socket to a address. bind() takes tuple of host and port. sock.bind((host, port)) #Listening at the address sock.listen(5) #5 denotes the number of clients can queue def clientthread(conn): #infinite loop so that function do not terminate and thread do not end. while True: #Sending message to connected client conn.send('Hi! I am server\n') #send only takes string #Receiving from client data = conn.recv(1024) # 1024 stands for bytes of data to be received print data while True: #Accepting incoming connections conn, addr = sock.accept() #Creating new thread. Calling clientthread function for this function and passing conn as argument. start_new_thread(clientthread,(conn,)) #start new thread takes 1st argument as a function name to be run, second is the tuple of arguments to the function. conn.close() sock.close()
Use the same client.py code for client from previous post.
#!usr/bin/python from socket import * host = 'localhost' # '127.0.0.1' can also be used port = 52000 sock = socket() #Connecting to socket sock.connect((host, port)) #Connect takes tuple of host and port #Infinite loop to keep client running. while True: data = sock.recv(1024) print data sock.send('HI! I am client.') sock.close()
Highlighted code is the changes done in the previous code we had.
What we have done in server.py is we took the communicating part inside the infinite while loop of function clientthread and using it in thread on line 32.
In client.py we took the communicating part inside the infinite while loop.
Everything else is explained in comments.
- Programs will not terminate by themselves because they will never come out of loop. So certainly you will receive error that socket is already in use.
- start_new_thread() takes 3 arguments. 3rd argument is kwargs which is of no use right now.
- 2nd argument of start_new_thread has to be a tuple. Tuples are fixed length array in python.
- Module threading can also be used for threading.
- start_new() is identical to start_new_thread().
- 5 in sock.listen(5) in server.py is of no use as every client will interact with server. May be it will be required when server can not handle more process.