Using Python for testing network connectivity

More and more Linux distributions have stopped shipping with basic networking tools such as telnet installed by default. ping is still available (sometimes), but to test if a server can communicate with another server on a particular port is now a challenge.

However, I find python is installed more-often-than-not, and ships with networking libraries that one can use for connectivity purposes. The following snippet checks for connectivity, in this case, HTTPS (443) to

$ python
import socket

Run it, and you’ll either get an exception thrown when connectivity fails, or no exception for a successful connection.

N.B. this won’t confirm application firewalls won’t block traffic, but as a basic connectivity test, this works fine.

Here is also a snazzy one liner to make a bash function if you need to run a large number of checks

c() { python <<<"import socket; s=socket.socket(); s.settimeout(5); s.connect(('$1',$2)) ; print 'Connection'"; }

And then use it in the following manner.

$ c 443
$ c 22

If you’re testing an internal network, set the timeout to something lower than 3 seconds, while if you’re testing a WAN or internet server, set it to a higher value.

Connectivity testing with Splunk’s inbuilt Python

I normally need to do connectivity tests as part of installing Splunk, which usually ships with python (although not with the Universal Forwarder). The python interpreter can be accessed from the command line with

/opt/splunk/bin/splunk cmd python

So the one liner becomes

c() { /opt/splunk/bin/splunk cmd python <<<"import socket; s=socket.socket(); s.settimeout(5); s.connect(('$1',$2)) ; print 'Connection'"; }