Standard service on TCP port 19 :) It spits out printable ASCII characters to anyone who asks as fast as it can.
General wisdom is that it is security hazard and not useful for anything on the open internet, but having some server with so called "simple TCP/IP services" in your internal testing LAN is useful for exactly this kind of debugging.
Edit: this whole debugging happened around january 2009, so at the time when chargen was long dead and certainly not a service offered by almost anyone on the internet.
Sadly, chargen is still alive on the open internet. It's not really a security hazard, but it does have a huge DDoS amplification factor, so it's not a good idea to run it on public IPs (and if you firewall it, do the world a favor and firewall the incoming requests, don't try to 'fix' it by firewalling the outgoing responses)
General wisdom is that it is security hazard and not useful for anything on the open internet, but having some server with so called "simple TCP/IP services" in your internal testing LAN is useful for exactly this kind of debugging.
Edit: this whole debugging happened around january 2009, so at the time when chargen was long dead and certainly not a service offered by almost anyone on the internet.