Python Tcp 断开检测

Question

I have a simpletcp example:

import socket
import time


TCP_IP = '127.0.0.1'
TCP_PORT = 81
BUFFER_SIZE = 1024

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((TCP_IP, TCP_PORT))

while True:
    s.send(bytes('hello', 'UTF-8'))
    time.sleep(1)

s.close()

How can I detect, if I lost the connection to the server, and how can I safely reconnect then?

Is it necessary to wait for answer to the server?

UPDATE:

import socket
import time

TCP_IP = '127.0.0.1'
TCP_PORT = 81
BUFFER_SIZE = 1024

def reconnect():
    toBreak = False
    while True:
        s.close()
        try:
            s.connect((TCP_IP, TCP_PORT))
            toBreak = True
        except:
            print ("except")        
        if toBreak:
            break
        time.sleep(1)


s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((TCP_IP, TCP_PORT))

while True:
    try:    
        s.send(bytes('hello', 'UTF-8'))
        print ("sent hello")
    except socket.error as e:
        reconnect()

    time.sleep(1)

s.close()

If I break the connection, it raises an error (does not really matter what), and goes to the reconnect loop. But after I restore the connection, the connect gives back this error:

OSError: [WinError 10038] An operation was attempted on something that is not a socket

If I restart the script, which calls the same s.connect((TCP_IP, TCP_PORT)), it works fine.

Answer 1

You'll get a socket.error : [Errno 104] Connection reset by peer exception (aka ECONNRESET ) on any call to send() or recv() if the connection has been lost or disconnected. So to detect that, just catch that exception:

while True:
    try:
        s.send(bytes('hello', 'UTF-8'))
    except socket.error, e:
        if e.errno == errno.ECONNRESET:
            # Handle disconnection -- close & reopen socket etc.
        else:
            # Other error, re-raise
            raise
    time.sleep(1)

Answer 2

Use a new socket when you attempt to reconnect.

def connect():
    while True:
        try:
            s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            s.connect((host, port))
            return s.makefile('w')
        except socket.error as e:
            log("socket error {} reconnecting".format(e))
            time.sleep(5)

dest = connect()
while True:
    line = p.stdout.readline()
    try:
        dest.write(line)
        dest.flush()
    except socket.error as e:
        log("socket error {} reconnecting".format(e))
        dest = connect()

Answer 3

Can you try that (I think that you does'not try socket.SO_REUSEADDR):

def open_connection():
    data0=''

    try:
        # Create a TCP/IP socket
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)

        # Connect the socket to the port where the server is listening
        server_address = ('192.168.0.100', 8000)
        sock.settimeout(10)     # TimeOut 5 secunde

        while True:

            try:
                sock.connect(server_address)
                message = 'new connection'
                sock.sendall(message)

                # Look for the response
                amount_received = 0
                data0=sock.recv(1024)
                amount_received = len(data0)
                return

            finally:
                wNET = 0
                pass

    except:
        sock.close()
        time.sleep(60)
        del data0

Answer 4

This is the code based on thread. The main tip is that the received buffer cannot be none, if the socket is connected.

import time
import socket
import threading

def connect():
    while True:
        try:
            s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            s.connect((host, port))
            s.settimeout(60)
            return s
        except socket.error as e:
            print("socket error {} reconnecting".format(e))
            time.sleep(5)

soc = connect()

def runSocket():
    global soc
    while True:
        try:
            recBuf = soc.recv(64)
            if recBuf == b'':    #remote server disconnect
                soc = connect()
            else:
                print(recBuf)
        except socket.timeout:
            print("Timeout")
        except Exception as e:
            print("other socket error {}".format(e))
            soc = connect()

socketThread = threading.Thread(target=runSocket)
socketThread.start()