SoulSpark
Software
www.skarnet.org

The tcpping program

tcpping is a basic utility that checks network connectivity by attempting TCP connections on a list of servers until one succeeds.

Interface

     tcpping [ -x | -X ] [ -T x+y ] ip:port [ ip:port ... ]

• tcpping attempts a TCP connection on every (ip, port) couple given on the command line. It exits 0 as soon as one succeeds.
• tcpping first tries all servers with a x-second timeout, then, if +y is specified, it performs a second pass with a y-second timeout. By default, x is 2 and y is 58.
• If all servers fail or timeout, tcpping exits 1.

Options

• -x : strict mode. tcpping will report failure for a server if a connection attempt fails with ECONNRESET. This is the default, and also the safest mode. To check network connectivity, first make sure that the conctacted ip/ports are open.
• -X : loose mode. tcpping will report success if a connection attempt fails with ECONNRESET.

Rationale: ECONNRESET means good probability of tcpping being able to reach ip, but nothing listening on port, which means that the machine at ip is alive and reachable anyway. But there's also a slim chance that some obnoxious filtering router along the way is rejecting your packets with TCP RST, and you are actually not able to reach ip.