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I was having some rare intermittent problems with Apache httpd talking to Tomcat.

I needed to determining if either the mod_jk in httpd or the Tomcat AJP connector was misbehaving. I did not easily find a script that performed an AJP ping. Therefore, I had to write one.

This is my first working version. The expected scalar is not used at this time. It is mainly there for documentation. Also, I probably won't remove the debug logging until it starts annoying me.

I stuck this on my tech blog, too.


#!/usr/bin/perl -w use warnings; use strict; use Socket; my ($remote, $port) = split /:/, shift @ARGV, 2; if (! $remote) { $remote = 'localhost'; } print "remote = $remote\n"; if (! $port) { $port = 8009; } print "port = $port\n"; my ($iaddr, $paddr, $proto); # If the port has anything other than numbers, we're assuming it is an # /etc/services name. if ($port =~ /\D/) { $port = getservbyname $port, 'tcp' ; } die "Bad port, stopped" unless $port; print "port = $port\n"; $iaddr = inet_aton($remote) || die "No host: $remote, stopped"; print "iaddr = $iaddr\n"; $paddr = sockaddr_in($port, $iaddr) || die "sockaddr: $!, stopped"; print "paddr = $paddr\n"; # Grab the number for TCP out of /etc/protocols. $proto = getprotobyname 'tcp' ; print "proto = $proto\n"; my $sock; # PF_INET and SOCK_STREAM are constants imported by the Socket module. + They # are the same as what is defined in sys/socket.h. socket $sock, PF_INET, SOCK_STREAM, $proto || die "socket: $!, stopped +"; print "sock = $sock\n"; print "BEFORE CONNECT\n"; connect $sock, $paddr || die "connect: $!, stopped"; print "AFTER CONNECT\n"; # This is the ping packet. For detailed documentation, see # # I stole the exact byte sequence from # +_id=438456 # instead of fully understanding the packet structure. my $ping = pack 'C5' # Format template. , 0x12, 0x34 # Magic number for server->container packets. , 0x00, 0x01 # 2 byte int length of payload. , 0x0A # Type of packet. 10 = CPing. ; my @ping_values = unpack 'C5', $ping; print "ping_values = " , join ' ', @ping_values , "\n"; # This is the expected pong packet. That is, this is what Tomcat send +s back # to indicate that it is operating OK. my $expected = pack 'C5' # Format template. , 0x41, 0x42 # Magic number for container->server packe +ts. , 0x00, 0x01 # 2 byte int length of payload. , 0x09 # Type of packet. 9 = CPong reply. ; syswrite $sock, $ping || die "syswrite: $!, stopped"; my $pong; $pong = 'empty'; print "BEFORE READ\n"; sysread $sock, $pong, 5 || die "read: $!, stopped"; print "AFTER READ\n"; my @pong_values = unpack 'C5', $pong; print "pong_values = " , join ' ', @pong_values , "\n"; close $sock || die "close: $!, stopped"; exit 0;

The following is an example of a good ping response.

me@mybox:~/ajp_ping $ time ./ localhost:8009 remote = localhost port = 8009 port = 8009 iaddr = paddr = proto = 6 sock = GLOB(0x506290) BEFORE CONNECT AFTER CONNECT ping_values = 18 52 0 1 10 BEFORE READ AFTER READ pong_values = 65 66 0 1 9 real 0m0.028s user 0m0.015s sys 0m0.013s

In reply to AJP ping by jffry

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