Implementing a websocket

Question

I found TooTallNate's Java-Websocket library. I am attempting to implement a client and server as a proof of concept to see if web sockets will solve a problem for us.

My client is my Ubuntu 12.04 Linux workstation. I wrote a websocket server application that listens for bindings on 4242. Then I run my client and attempt to connect. I captured the communication using wireshark:

214 9.064163    192.168.1.81    192.168.20.50   TCP 74  43413 > 4242 [SYN] Seq=0 Win=14600 Len=0 MSS=1460 SACK_PERM=1 TSval=185839 TSecr=0 WS=128
215 9.064191    192.168.20.50   192.168.1.81    TCP 54  4242 > 43413 [RST, ACK] Seq=1 Ack=1 Win=0 Len=0

My question is, why would the packet be refused so quickly? I don't believe I'm running a firewall, but if it were a firewall, unregistered ports generally just get ignored instead of shutdown within a few picoseconds. Does anyone know what this means?

Answer 1

You should first of all check whether the server is actually listening, using netstat:

netstat -ln

or, using the long form parameters

netstat --listening --numeric

If you don't see anything listing on the correct port, something went wrong during setup on the server side.