Fortunately, a few basic tools found on almost any Linux system can make this easy.
The watch utility runs whatever command you provide it at the interval you specify. Here's the world's cheapest realtime clock.
$ watch -n 1 'date'Netcat is too versatile to cover in depth in this post, but one of its most basic capabilities is accepting data via standard input, sending that data to a host / port combination of your choosing, and then dumping the result to standard output.
$ printf "HEAD / HTTP/1.0\r\n\r\n" | nc google.com 80 | grep Server Server: gwsThe above command takes the HTTP HEAD request from printf, sends it to netcat, which then passes it on to google.com on port 80. The results are printed to standard output, and the grep command limits the result output to the server returned (in this case gws).
Combining these two commands provides a ton of utility. Here are two useful examples that I use regularly.
1) Monitoring Gearman queues in realtime
watch -n 1 '(echo status; sleep 0.1) | nc localhost 4730' publishMessage 4 0 1 consumeMessage 7 0 8 archiveMessage 28 0 12 .2) Monitoring memcached get/set commands in realtime
watch -n 1 '(echo stats; sleep 0.1) | nc localhost 11211 | grep cmd' STAT cmd_get 506 STAT cmd_set 8 STAT cmd_flush 0 STAT cmd_touch 0 STAT auth_cmds 0