CODEWITHSUNDEEP
pythonudpclient-server
Aleksej_Shherbak
Aleksej_Shherbak

Reputation: 3078

Python UDP socket don't work after making first connection

I am traing to make simple application on python that works with sockets and use UDP protocol. I have a client.py and server.py. I whant to send messages from client to server in infinity loop and catch resive message from server. For making this I have following code:

server.py

import socket

serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
host = "127.0.0.1"
port = 8000
print(host)
print(port)
serversocket.bind((host, port))

serversocket.listen(5)
print('server started and listening')
while 1:
    (clientsocket, address) = serversocket.accept()
    print("connection found!")
    data = clientsocket.recv(1024).decode()
    print(data)
    r = 'I can hear you by UDP!!!!'
    clientsocket.send(r.encode())

client.py

import socket

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
host = "127.0.0.1"
port = 8000
addr = (host, port)
s.connect(addr)


def send(user_input):
    s.sendto(user_input.encode(), addr)
    data = s.recv(1024).decode()
    print('Server tell that: ', data)


while 1:
    if input('Exit? (y/n)') == 'y':
        break
    i = input('>> ')
    send(i)

s.close()

It's work correctly, but when i try to send message second time, my program make stop on line

s.sendto(user_input.encode(), addr)

I don't understand what's happening in this moment.

Upvotes: 0

Views: 2428

Answers (1)

Sphinx
Sphinx

Reputation: 10729

If you'd like to build server/client for UDP, you need to read the documents carefully to prevent from using the APIs which are for connection-oriented protocols.

Below is one working sample for UDP: (I added some comments in the codes, then you will see why adjusted them).

Server:

For one UDP server, you need to initialize with one socket socket.SOCK_DGRAM instead of SOCK_STREAM, then bind the port you'd like.

import socket

#The type of communications between the two endpoints, typically SOCK_STREAM for connection-oriented protocols and SOCK_DGRAM for connectionless protocols.
serversocket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
host = "127.0.0.1"
port = 8000
print(host)
print(port)
serversocket.bind((host, port))

#serversocket.listen(5)  #--This method sets up and start TCP listener.
print('server started and listening')
while 1:
    #(clientsocket, address) = serversocket.accept() #---This passively accept TCP client connection, waiting until connection arrives (blocking)
    #print("connection found!")
    #data = clientsocket.recv(1024).decode() #This method receives TCP message
    data, addr = serversocket.recvfrom(2048)
    print(data)
    r = 'I can hear you by UDP!!!!'
    serversocket.sendto(r.encode(), addr)
serversocket.close()

Client:

For one UDP client, you need to initialize one socket with socket.SOCK_DGRAM instead of SOCK_STREAM, then uses sendto to send the data to the server.

import socket
#The type of communications between the two endpoints, typically SOCK_STREAM for connection-oriented protocols and SOCK_DGRAM for connectionless protocols.
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
host = "127.0.0.1"
port = 8000
addr = (host, port)
#s.connect(addr) #---This method actively initiates TCP server connection.


def send(user_input):
    s.sendto(user_input.encode(), addr)
    data = s.recvfrom(1024).decode()
    print('Server tell that: ', data)


while 1:
    if input('Exit? (y/n)') == 'y':
        break
    i = input('>> ')
    send(i)

s.close()

For more details:

Check Python Socket

Upvotes: 1

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