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Socket Programming with Multi-threading in Python

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Prerequisite : Socket Programming in Python, Multi-threading in Python
Socket Programming-> It helps us to connect a client to a server. Client is message sender and receiver and server is just a listener that works on data sent by client.
What is a Thread? 
A thread is a light-weight process that does not require much memory overhead, they are cheaper than processes.
What is Multi-threading Socket Programming? port on your computer
Multithreading is a process of executing multiple threads simultaneously in a single process.
Multi-threading Modules : 
A _thread module & threading module is used for multi-threading in python, these modules help in synchronization and provide a lock to a thread in use. 

from _thread import *
import threading

A lock object is created by-> 

print_lock = threading.Lock()

A lock has two states, “locked” or “unlocked”. It has two basic methods acquire() and release(). When the state is unlocked print_lock.acquire() is used to change state to locked and print_lock.release() is used to change state to unlock.
The function thread.start_new_thread() is used to start a new thread and return its identifier. The first argument is the function to call and its second argument is a tuple containing the positional list of arguments.
Let’s study client-server multithreading socket programming by code- 
Note:-The code works with python3. 
Multi-threaded Server Code 


# import socket programming library
import socket
# import thread module
from _thread import *
import threading
print_lock = threading.Lock()
# thread function
def threaded(c):
    while True:
        # data received from client
        data = c.recv(1024)
        if not data:
            # lock released on exit
        # reverse the given string from client
        data = data[::-1]
        # send back reversed string to client
    # connection closed
def Main():
    host = ""
    # reserve a port on your computer
    # in our case it is 12345 but it
    # can be anything
    port = 12345
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.bind((host, port))
    print("socket binded to port", port)
    # put the socket into listening mode
    print("socket is listening")
    # a forever loop until client wants to exit
    while True:
        # establish connection with client
        c, addr = s.accept()
        # lock acquired by client
        print('Connected to :', addr[0], ':', addr[1])
        # Start a new thread and return its identifier
        start_new_thread(threaded, (c,))
if __name__ == '__main__':

Console Window:
socket binded to port 12345
socket is listening
Connected to : : 11600

Client Code 


# Import socket module
import socket
def Main():
    # local host IP ''
    host = ''
    # Define the port on which you want to connect
    port = 12345
    s = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
    # connect to server on local computer
    # message you send to server
    message = "shaurya says geeksforgeeks"
    while True:
        # message sent to server
        # message received from server
        data = s.recv(1024)
        # print the received message
        # here it would be a reverse of sent message
        print('Received from the server :',str(data.decode('ascii')))
        # ask the client whether he wants to continue
        ans = input('\nDo you want to continue(y/n) :')
        if ans == 'y':
    # close the connection
if __name__ == '__main__':

Console Window:
Received from the server : skeegrofskeeg syas ayruahs

Do you want to continue(y/n) :y
Received from the server : skeegrofskeeg syas ayruahs

Do you want to continue(y/n) :n

Process finished with exit code 0

This article is contributed by SHAURYA UPPAL. If you like GeeksforGeeks and would like to contribute, you can also write an article using or mail your article to See your article appearing on the GeeksforGeeks main page and help other Geeks.
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Last Updated : 14 Jul, 2022
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