Python Socket Get Last Error
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Except Socket.error E Syntaxerror Invalid Syntax
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Socket Connect Exception Python
it only takes a minute: Sign up Python handling specific error codes? up vote 17 down vote favorite 3 Hey I'm wondering how to handle specific error codes. For example, [Errno 111] Connection refused I want to catch this specific error in the socket module and print something. python sockets exception exception-handling share|improve this question asked Mar 1 '11 at socket error handling 22:25 AustinM 26041224 add a comment| 3 Answers 3 active oldest votes up vote 23 down vote accepted If you want to get the error code, this seems to do the trick; import errno try: socketConnection() except socket.error, v: errorcode=v[0] if errorcode==errno.ECONNREFUSED: print "Connection Refused" You can look up errno error codes. share|improve this answer edited Aug 10 at 15:43 Flimm 24k107081 answered Mar 1 '11 at 22:40 utku.zih 2,81921741 5 On OSX, ECONNREFUSED appears to be 61 not 111, so hard-coding the value 111 would be a bad idea for portability. –jchl Mar 1 '11 at 22:46 You are absolutely right. I am sure that there are more cases like that. –utku.zih Mar 1 '11 at 22:48 It's important to have an else: raise, otherwise all other error codes will be silently ignored! –jtpereyda Sep 3 at 22:56 add a comment| up vote 23 down vote On Unix platforms, at least, you can do the following. import socket, errno try: # Do something... except socket.error as e: if e.errno == errno.ECONNREFUSED: #
Server with Select A Long-Lived Echo Client The Threading Module Code Index License This work is licensed under a Creative Commons License. The Socket Module Catching Exceptions In the previous examples, we have not checked for any exceptions that
Except Socket Error Msg Invalid Syntax
could be raised by methods in the socket module. One clear example is when
Python Socket Error 10054
the server tries to bind its socket to a particular port. Only one process is allowed to bind to each port; python import errno if this port is already being used then an exception is raised. Here is the modified echo server that catches some of these exceptions (echoserver-simple-exceptions.py): #!/usr/bin/env python """ A simple echo server that handles http://stackoverflow.com/questions/5161167/python-handling-specific-error-codes exceptions """ import socket host = '' port = 50000 backlog = 5 size = 1024 s = None try: s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.bind((host,port)) s.listen(backlog) except socket.error, (value,message): if s: s.close() print "Could not open socket: " + message sys.exit(1) while 1: client, address = s.accept() data = client.recv(size) if data: client.send(data) client.close() The part that has changed is where the socket is initialized: s = None try: s http://ilab.cs.byu.edu/python/socket/exceptions.html = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.bind((host,port)) s.listen(backlog) except socket.error, (value,message): if s: s.close() print "Could not open socket: " + message sys.exit(1) This code is surrounded by a try-except statement, and the except portion contains two values: the socket.error exception, and its return value. The socket.error exception is raised for socket-related errors; the socket module defines several other exceptions for address-related errors. The return value of the socket is a tuple consisting of an error code and message. Try running this server twice, and the second time you should be able to see the exception that is caught. Run the original server twice if you want to see what happens when the exception is not caught. As another example, here is the echo client modified to catch some exceptions (echoclient-simple-exceptions.py): #!/usr/bin/env python """ A simple echo client that handles some exceptions """ import socket import sys host = 'localhost' port = 50000 size = 1024 s = None try: s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect((host,port)) except socket.error, (value,message): if s: s.close() print "Could not open socket: " + message sys.exit(1) s.send('Hello, world') data = s.recv(size) s.close() print 'Received:', data Try running this version (and the original) without running the server at all, and see the exception that is caught.
interface¶ Source code: Lib/socket.py This module provides access to the BSD socket interface. It is available on all modern Unix systems, Windows, MacOS, and probably additional platforms. Note Some behavior may be platform dependent, since https://docs.python.org/3/library/socket.html calls are made to the operating system socket APIs. The Python interface is a straightforward transliteration of the Unix system call and library interface for sockets to Python's object-oriented style: the http://www.digi.com/wiki/developer/index.php/Handling_Socket_Error_and_Keepalive class="pre">socket() function returns a socket object whose methods implement the various socket system calls. Parameter types are somewhat higher-level than in the C interface: as with read() and write() operations on socket error Python files, buffer allocation on receive operations is automatic, and buffer length is implicit on send operations. See also Module socketserver Classes that simplify writing network servers. Module ssl A TLS/SSL wrapper for socket objects. 18.1.1. Socket families¶ Depending on the system and the build options, various socket families are supported by this module. The address format required by a particular socket object python socket error is automatically selected based on the address family specified when the socket object was created. Socket addresses are represented as follows: The address of an AF_UNIX socket bound to a file system node is represented as a string, using the file system encoding and the 'surrogateescape' error handler (see PEP 383). An address in Linux's abstract namespace is returned as a bytes-like object with an initial null byte; note that sockets in this namespace can communicate with normal file system sockets, so programs intended to run on Linux may need to deal with both types of address. A string or bytes-like object can be used for either type of address when passing it as an argument. Changed in version 3.3: Previously, AF_UNIX socket paths were assumed to use UTF-8 encoding. Changed in version 3.5: Writable bytes-like object is now accepted. A pair (host, port) is used for the AF_INET address family, where host is a string representing either a hostname in Internet domain notation like 'daring.cwi.nl' or an IPv4 address like '100.50.200.5', and port is an integer. For AF_INET6 address family, a four-tuple
exists and that crashing due to exceptions is helpful education for you. trying to locate realistic examples often pushes you into complex examples using hundreds of lines of code to do real work. So here is a simple-dummy example TCP client application which runs on either a PC or Digi product: It creates the socket It sets the socket timeout to 5.0 seconds, this means non-blocking and all requests will fault in 5.0 seconds unless they succeed. It tests and enables the TCP Keepalive - which by default is OFF on most systems (Windows, Linux and Digi Python) This test is NOT required; it is here merely to show how it is done. It tries to open (connect) to a fixed IP address and TCP port 2101, which either succeeds rapidly - or fails in 5.0 seconds. "except socket.error" traps the error and causes the code to sleep 5 more seconds, then restart at socket creation. if the socket is open, it waits 5 seconds for up to 6 bytes of data, and throws an exception if socket errors or no data is received. This block has two-level error trapping: "except socket.timeout" traps the no-data error and loops up to try receiving again. Note that a robust program design would keep track of how frequently (or long) this 'no data' continues. In many designs, a TCP socket sitting idle for more than a few minutes might be best closed. "except socket.error" traps any remaining error, and exits the inner "while True:" and restarts creating the socket. To use this example, set the IP address to any Digi TS/DS with TCP Sockets active. Then by powering up or down the Digi TS/DS you can cause the connect(('x.x.x.x',2101) to succeed or fail. Sending simple ASCII data into the serial port of the Digi TS/DS would enable you to force or skip the "socket.timeout" try-except clause. TCP Keepalive So how does your Python code understand if no data means the TCP peer is being quiet - or if the TCP socket has gone away? The normal answer is that eventually a socket error will cause the "socket.error" clause to execute. However, that could easily be hours (or forever) after the socket fails. By default sockets in your Digi Python application (as well as Windows or Linux) open with TCP keepalives turned off