Handling a timeout error in python sockets
Solution 1
from foo import *
adds all the names without leading underscores (or only the names defined in the modules __all__
attribute) in foo
into your current module.
In the above code with from socket import *
, you just want to catch timeout
as you've pulled timeout
into your current namespace.
from socket import *
pulls in the definitions of everything inside of socket
, but it doesn't add socket
itself.
try:
# Socket stuff
except timeout:
print 'caught a timeout'
Many people consider import *
problematic and try to avoid it. This is because common variable names in two or more modules that are imported in this way will clobber one another.
For example, consider the following three Python files:
# File "a.py"
def foo():
print "this is a's foo function"
# File "b.py"
def foo():
print "this is b's foo function"
# File "yourcode.py"
from a import *
from b import *
foo()
If you run yourcode.py
, you'll see just the output "this is b's foo function".
For this reason I'd suggest either importing the module and using it or importing specific names from the module:
For example, your code would look like this with explicit imports:
import socket
from socket import AF_INET, SOCK_DGRAM
def main():
client_socket = socket.socket(AF_INET, SOCK_DGRAM)
client_socket.settimeout(1)
server_host = 'localhost'
server_port = 1234
while(True):
client_socket.sendto('Message', (server_host, server_port))
try:
reply, server_address_info = client_socket.recvfrom(1024)
print reply
except socket.timeout:
# More code
It is just a tiny bit more typing, but everything's explicit and it's pretty obvious to the reader where everything comes from.
Solution 2
I had enough success just catching socket.timeout
and socket.error
; although socket.error can be raised for lots of reasons. Be careful.
import socket
import logging
hostname = 'google.com'
port = 443
try:
sock = socket.create_connection((hostname, port), timeout=3)
except socket.timeout as err:
logging.error(err)
except socket.error as err:
logging.error(err)
Solution 3
When you do from socket import *
, the Python interpreter is loading a socket
module to the current namespace. Thus you can use the module's members as if they were defined within your current Python module.
When you do import socket
, a module is loaded in a separate namespace. When you are accessing its members, you should prefix them with a module name. For example, if you want to refer to a socket
class, you will need to write client_socket = socket.socket(socket.AF_INET,socket.SOCK_DGRAM)
.
As for the problem with timeout, all you need to do is to change except socket.Timeouterror:
to except timeout:
, since timeout
class is defined inside socket
module and you have imported all its members to your namespace.
Solution 4
Here is a solution I use in one of my projects.
File network_utils.telnet
import socket
from timeit import default_timer as timer
def telnet(hostname, port=23, timeout=1):
start = timer()
connection = socket.socket()
connection.settimeout(timeout)
try:
connection.connect((hostname, port))
end = timer()
delta = end - start
except (socket.timeout, socket.gaierror) as error:
logger.debug('telnet error: ', error)
delta = None
finally:
connection.close()
return {
hostname: delta
}
Tests
def test_telnet_is_null_when_host_unreachable(self):
hostname = 'unreachable'
response = network_utils.telnet(hostname)
self.assertDictEqual(response, {'unreachable': None})
def test_telnet_give_time_when_reachable(self):
hostname = '127.0.0.1'
response = network_utils.telnet(hostname, port=22)
self.assertGreater(response[hostname], 0)
Greg Brown
Updated on May 11, 2020Comments
-
Greg Brown about 4 years
I am trying to figure out how to use the try and except to handle a socket timeout.
from socket import * def main(): client_socket = socket(AF_INET,SOCK_DGRAM) client_socket.settimeout(1) server_host = 'localhost' server_port = 1234 while(True): client_socket.sendto('Message',(server_host,server_port)) try: reply, server_address_info = client_socket.recvfrom(1024) print reply except socket.Timeouterror: #more code
The way I added the socket module was to import everything, but how do I handle exceptions in the docs it says you can use socket.timeouterror, but that doesn't work for me. Also, how would I write the try exception block if I did
import socket
? Can someone also explain the difference in the imports. -
stephenbez over 10 yearsI think you mean
socket.timeout
instead ofsocket.Timeouterror
: docs.python.org/2/library/socket.html#socket.timeout -
Peter Mortensen about 2 yearsAn explanation would be in order, especially in light of the previous answers. E.g., what is the idea/gist? From the Help Center: "...always explain why the solution you're presenting is appropriate and how it works". Please respond by editing (changing) your answer, not here in comments (without "Edit:", "Update:", or similar - the answer should appear as if it was written today).