12th October 2003
Is your server working? The best way to find out is to try connecting
a client to it, according to the protocol that it speaks. But there is
a faster way to check for simple problems. This program is a simple
server tester. It tries to connect to the TCP/IP server but does not
transfer any data. It is intended to be used in scripts that check
a list of servers, and it can help to detect the following conditions:
However, this method of testing has limits. There is no validation of
the protocol used by the server, nor any testing of the data transfer
that the server and client would normally perform. So pung cannot be used to
- total server failure, due to power or operating system failure,
- server listener failure, such as a missing daemon or inetd,
- network connectivity issues, such as broken links, faulty routes,
- some types of domain name resolution problems.
Since most failures fall into the first list rather than the second, Pung
has some potential use. Based on the return status code and output, actions
can be taken by regular scripts. Quozl uses a script that compares a list
of Pung results with a known-good list, and if there are differences
launching an xterm that displays them.
- failures to activate the program specified by inetd,
- failures that occur during client/server negotiation,
- network performance problems, such as oscillating routes,
- subversion of server content,
- name resolution to a host with the same service listening,
checker.csh > latest.txt
sdiff -s -l latest.txt normal.txt | \
grep "\|" | \
cut -f 1 -d\| > differences.txt
set LINES=`wc -l differences.txt`
if ( "$LINES" != "0" ) then
xterm -T checker -bg black -fg red \
-e view differences.txt
The script checker.csh (not shown) contains a list of Pung invokations
for critical servers. It is run once when all servers are working and
the results saved in normal.txt. The script above performs the check
again, compares the output, tests the differences count, and launches the
xterm to view the differences.
Pung version 1.1, Copyright (C) 2003 James Cameron
Pung comes with ABSOLUTELY NO WARRANTY; for details see source.
This is free software, and you are welcome to redistribute it
under certain conditions; see source for details.
Usage: pung host port [timeout]
Attempts a TCP/IP connection only to the host on the given port,
and displays the result on standard output. No data is
transferred. Returns a status code;
0 = Connection accepted
1 = Non-existent host
2 = Non-existent service
3 = connect() call failed
Pung is intended for use in automated testing of TCP/IP servers.
The host and port arguments may be alphabetic or numeric.
Examples: pung localhost telnet
pung 127.0.0.1 23
The optional timeout in seconds may be used to restrict the time
spent waiting for a connection to occur.
What about UDP, and can I get it to mail me?
This program is a point solution; it is up to you to add the
components you need. If you are looking for a more extensive
solution, have a look at the package netsaint. It is capable of this
and much more.
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