Python socket connection exception

问题:

I have a socket-connection going on and I wanna improve the exception handling and Im stuck. Whenever I use the socket.connect(server_address) function with an invalid argument the program stops, but doesnt seem to throw any exceptions. Heres my code

import socket import sys import struct class ARToolkit():      def __init__(self):         self.x = 0         self.y = 0         self.z = 0         self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)         self.logging = False       def connect(self,server_address):         try:             self.sock.connect(server_address)         except socket.error, msg:             print "Couldnt connect with the socket-server: %s\n terminating program" % msg             sys.exit(1)       def initiate(self):         self.sock.send("start_logging")      def log(self):         self.logging  = True           buf = self.sock.recv(6000)         if len(buf)>0:             nbuf = buf[len(buf)-12:len(buf)]             self.x, self.y, self.z = struct.unpack("

The class maybe looks a bit wierd but its used for receiving coordinates from another computer running ARToolKit. Anyway, the issue is at the function connect():

def connect(self,server_address):         try:             self.sock.connect(server_address)         except socket.error, msg:             print "Couldnt connect with the socket-server: %s\n terminating program" % msg             sys.exit(1) 

If I call that function with a random IP-address and portnumber the whole program just stops up at the line:

self.sock.connect(server_address) 

The documentation I've read states that in case of an error it will throw a socket.error-exception. I've also tried with just:

except Exception, msg: 

This, if I'm not mistaken, will catch any exceptions, and still it yields no result. I would be very grateful for a helping hand. Also, is it okay to exit programs using sys.exit when an unwanted exception occurs?

Thank you

回答1:

If you have chosen a random, but valid, IP address and port, socket.connect() will attempt to make a connection to that endpoint. By default, if no explicit timeout is set for the socket, it will block while doing so and eventually timeout, raising exception socket.error: [Errno 110] Connection timed out.

The default timeout on my machine is 120 seconds. Perhaps you are not waiting long enough for socket.connect() to return (or timeout)?

You can try reducing the timeout like this:

import socket  s = socket.socket() s.settimeout(5)   # 5 seconds try:     s.connect(('123.123.123.123', 12345))         # "random" IP address and port except socket.error, exc:     print "Caught exception socket.error : %s" % exc 

Note that if a timeout is explicitly set for the socket, the exception will be socket.timeout which is derived from socket.error and will therefore be caught by the above except clause.

回答2:

The problem with your last general exception is the colon placement. It needs to be after the entire exception, not after the except statement. Thus to capture all exceptions you would need to do:

except Exception,msg: 

However from Python 2.6+ you should use the as statement instead of a comma like so:

except Exception as msg: 

I was able to run the code fine (note you need to throw in a tuple to the connect method). If you want to specifically catch only socket errors then you would need to except the socket.error class. Like you have:

except socket.error as msg: 

If you want to make sure that a tuple is entered simply add another exception loop:

except socket.error as msg:     print "Socket Error: %s" % msg except TypeError as msg:     print "Type Error: %s" % msg 

文章来源: Python socket connection exception