如果客户端与服务器断开连接，如何断开连接？

Question

I have written a server and a client and if I close my client and connect again my clients list on the server just stacks up. First time I disconnect I print out whats on the list so first I get this:

{612: <socket.socket fd=612, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=0, laddr=('192.168.1.77', 22050), raddr=('192.168.1.77', 53531)>

Second time I connect it just stacks up so it looks like this:

{612: <socket.socket fd=612, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=0, laddr=('192.168.1.77', 22050), raddr=('192.168.1.77', 53531)>, 620: <socket.socket fd=620, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=0, laddr=('192.168.1.77', 22050), raddr=('192.168.1.77', 53532)>}

How do I make it so it just drops the connection? Here is the server code:

import socket
import threading
from _thread import *
from threading import Thread

clients = {}

def message(c):
    while True:
        try:
            data = c.recv(1024).decode("utf-8")
            print("Recieved from: " + str(data))
            if not data:
                print("Client Disconnected.")
                print(clients)
                break

            # skicka meddelanden till client
            for client in clients.values():
                try:
                    if client == c:
                        continue
                    client.sendall(data.encode("utf-8"))
                except ConnectionAbortedError:
                    print("[!] Connection aborted ")
                    print(str(clients))
                except ConnectionResetError:
                    print("[!] Connection reset error ")
                    print(str(clients))
        except ConnectionResetError:
            print("[!] - An existing connection was forcibly closed by the remote host. \n")
            break

def listener():
    host = "192.168.1.77"
    port = 22050
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.bind((host, port))
    s.listen(5)
    print("\nServer has started.\n\n" + "Host: " + host + "\nPort: " + str(port))
    print("______________________________________________________________________\n")
    while True:
        c, addr = s.accept()
        print(str(addr) + " has connected.")
        clients[c.fileno()] = c
        threading.Thread(target=message, args=(c,)).start()


if __name__ == '__main__':
    listenerthread = Thread(target=listener())
    listenerthread.start
    #listener()

And here is the client code:

import socket
import os
from multiprocessing import Process
from threading import Thread
import sys

print("... Awaiting connection from server ...")

host = "192.168.1.77"
port = 22050

try:
    s = socket.socket()
    s.connect((host, port))
except ConnectionRefusedError:
    print("Server is down.")
    sys.exit()
try:
    print("Connected!")

    def send():
        while True:
           message = input("-> ")
           s.send(message.encode("utf-8"))
           #recieve = s.recv(1024).decode("utf-8")
           #print("- Server: " + recieve)

    def recv():
        recieve = s.recv(1024).decode("utf-8")
        print("\n" + "Server: " + recieve)

#    while message !="quitclient":
#        s.send(message.encode("utf-8"))
#        recieve = s.recv(1024).decode("utf-8")
#        print("Recieved from server: " + recieve)
#        message = input("-> ")
#    s.close()

except ConnectionResetError:
    print("Disconnected!")
    input("Press enter to exit...")
    quit()
sendthread = Thread(target=send)
recvthread = Thread(target=recv)

sendthread.start()
recvthread.start()

The client code is just a cli version of the GUI client code I have (not writing it since its way too long) but its the same code. On the GUI version I have a disconnect button that looks like this:

def Disconnect():
    s.shutdown(socket.SHUT_RDWR)
    s.close()

What am I doing wrong here?

Answer 1

The clients dictionary is only added to, never removed. Something like the following should work. Catch any exception and drop out to remove the key from the dictionary.

def message(c):
    try:
        while True:
            data = c.recv(1024).decode("utf-8")
            print("Received from: " + str(data))
            if not data:
                print("Client Disconnected.")
                print(clients)
                break

            # skicka meddelanden till client
            for client in clients.values():
                if client == c:
                    continue
                client.sendall(data.encode("utf-8"))
    except Exception as e:
        print(e)
    clients.pop(c.fileno())
    print(clients)

As an aside, the code below never starts a thread due to needing start() not start . The listener starts because it is called in target=listener() , which should be target=listener :

if __name__ == '__main__':
    listenerthread = Thread(target=listener())
    listenerthread.start
    #listener()

But starting a thread to call listener is not needed. Just use:

if __name__ == '__main__':
    listener()

You'll also eventually have a problem with messages. TCP is a streaming protocol, so you can't assume each recv receive exactly what send sent. send doesn't guarantee it will send every byte either...check the return value or use sendall . Small messages sent slowly may never show the problem, but send large messages full of multi-byte UTF-8-encoded characters and you'll get an error. See this recent answer of mine for a simple way to solve it.