Hi there! Anybody home? Quite often, admins need to make sure that at least the physical connection between two computers is still up – or back up. Obviously, ping is the tool of choice when it comes to proving or refuting accessibility. However, there are cases in which a firewall blocks the ICMP ping. Anyone with a modicum of knowledge can save the energy they would otherwise waste cussing and instead type:

nmap -p <port>

Don't cheer too soon, though, because often an intrusion prevention system blocks the Nmap signature of the workaround.

Paping [1] establishes a connection to a configurable port and immediately terminates it again. This works almost anywhere. It measures the round-trip time in milliseconds, just like ping. The simplest form of the call is very intuitive:

paping <target>

The tool can handle optional parameters, too (Figure 1); a typical call looks like:

paping www.google.com -p 80 -c 4

The -p parameter specifies the TCP port to target – 80 in this case – which will return the expected results for a web server. By using -c <no_of_checks>, I can define how often Paping checks out the target.

Figure 1: Paping pinging port 80 on Google's web server. No matter what lies in between, the web server will respond – after an average of 48ms in this case.

Give Him a Break!

If you know that your target resides on a particularly slow or fast line, you might want to tune the -t <timeout_in_msec> parameter; that is, the time in which Paping abandons its task. Without the option, the tool throws in the towel after 1 second (1,000ms).

Purists who find the attractive output shown in Figure 1 too psychedelic, or cave dwellers sitting in front of terminals or dot matrix printers, can use the --nocolor option. This kicks Paping back into the monochrome era.

So, will Paping's programmer Mike Lovell be building an API for Android apps? No way: The open source tool has apparently reached the end of its design cycle – nobody has touched the C++ code for two years, but that is not surprising for such a simple tool.

If your Linux distribution does not include Paping in its repositories, you can grab the source or Linux version built for 32- and 64-bit systems [1].

Firewall in the way during ping testing? I don't care!