Python - Socket Communication, multiple messages

Question

I'm stuck on this socket communication, I've looked everywhere but I haven't found an answer yet.

THE PROBLEM: I can only send 1 message from the client before it either gives me an error or ends the script. I need to be able to send multiple messages to the server.

The server side (shown below) should be fine:

# Echo server program
import socket
import time
import os
#-----------------------------------------------------------------------------------------------------------------------
today = time.strftime('%Y.%m.%d')
logFileName = "log - " + today + ".txt"
HOST = '10.0.0.16' 
PORT = 8080 # Reserve a port for your service
BUFFER_SIZE = 1024 
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) # Create a socket object
s.bind((HOST, PORT)) # Bind to the port
def print_write(text):
 log.write(time.strftime("%H:%M:%S") + " | " + text)
 log.write("\n")
 print text
#-----------------------------------------------------------------------------------------------------------------------
if os.path.isfile(logFileName) is True:
 log = open(logFileName, 'a+')
 print_write("[SERVER] Log for " + today + " already exists.")
 print_write("[SERVER] Starting comms")
else:
 print "[SERVER] Log doesn't exist"
 log = open(logFileName, 'a+') # Create file -> log - %date%.txt
 print_write("[SERVER] Log created")
while True:
 s.listen(1)
 conn, addr = s.accept()
 data = conn.recv(BUFFER_SIZE)
 if data == "Comms Shutdown":
 print_write("------ REMOTE SHUTDOWN ------")
 conn.close()
 raise SystemExit
 else:
 print_write("[COMMS] " + str(addr) + " says: " + data)
log.close()

Sorry if it's very messy and confusing but i don't have much time to finish this project, if you have any question just ask.

For the client side I don't have much but here, I'll give you this:

import socket
HOST = '10.0.0.16' # The remote host
PORT = 8080 # The same port as used by the server
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST, PORT))
while True:
 msg = raw_input()
 s.sendall(msg)
 print msg

I know it doesn't work, it's just to give you an idea of what I need.

Thank you in advance.

• noteness: Your server code only calls recv one time before looping again, you should use a while loop or something like that to call recv multiple times before opening a new connection..

Answer 1

The problem is, that you only read the first message from each open connection before moving on to the next. The accept() methods waits for a new connection and gives you the information needed when a new one comes in. the recv() method on the other hand, receives data from a existing connection and waits if there is none. If you want to receive multiple messages from a single client, you can just wait for the first connection and then wait for data with recv(). This could look like this:

s.listen(1)
conn, addr = s.accept()
while True:
 data = conn.recv(BUFFER_SIZE)
 if data == "Comms Shutdown":
 print_write("------ REMOTE SHUTDOWN ------")
 conn.close()
 raise SystemExit
 else:
 print_write("[COMMS] " + str(addr) + " says: " + data)

If you want to be able to also manage multiple clients, you will have to create a thread for each one from a while loop waiting for new connections. This is a bit more complicated:

def client_handler(conn):
 while True:
 data = conn.recv(BUFFER_SIZE)
 if data == "Comms Shutdown":
 print_write("------ REMOTE SHUTDOWN ------")
 conn.close()
 raise SystemExit 
 # this will kill the server (remove the line above if you don't want that)
 else:
 print_write("[COMMS] " + str(addr) + " says: " + data)
while True:
 s.listen(1)
 conn, addr = s.accept()
 recv_thread = threading.Thread(target=client_handler, args=(conn, ))
 recv_thread.start()

All this code is untested. Be aware, that I omitted the logging part and the socket creation part as well as all imports.

• de_fault: Exactly what I was looking for! Great, thank you very much.