I suspect this is either a very simple question, or a very complex one.

I have a headless server running ubuntu 10.04 that I can ssh into. I have full root access to the system. I am trying to set up an ssh tunnel to allow me to vnc to the system (but that isn't my question.

I have vnc running on port 5903, here is the netstat output for that:

Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 0.0.0.0:5903            0.0.0.0:*               LISTEN      7173/Xtightvnc
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      
465/sshd

But when I try to telnet to that port, from within the same system and login, I get unable to connect errors

# telnet localhost 5903
Trying ::1...
Trying 127.0.0.1...
telnet: Unable to connect to remote host: Connection timed out

I am able to telnet to port 22 (as a verification)

~# telnet localhost 22
Trying ::1...
Connected to localhost.
Escape character is '^]'.
SSH-2.0-OpenSSH_5.3p1 Debian-3ubuntu7

I have tried to open up any possible ports using ufw (probably clumsy fashion)

# ufw status numbered
Status: active

     To                         Action      From
     --                         ------      ----
[ 1] 5903                       ALLOW IN    Anywhere
[ 2] 22                         ALLOW IN    Anywhere

What else might be blocking this connection locally?

Thank you,

Edit:

The only reference to port 5903 in iptable -L -n is this:

Chain ufw-user-input (1 references)
target     prot opt source               destination
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0           tcp dpt:5903
ACCEPT     udp  --  0.0.0.0/0            0.0.0.0/0           udp dpt:5903
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0           tcp dpt:22
ACCEPT     udp  --  0.0.0.0/0            0.0.0.0/0           udp dpt:22
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0           tcp dpt:8080
ACCEPT     udp  --  0.0.0.0/0            0.0.0.0/0           udp dpt:8080

I can post the whole output if that will be useful.

hosts.allow and hosts.deny both contain only comments.

Re-Edit: Some other questions pointed me to nmap, so I ran a portscan through that utility:

# nmap -v -sT localhost -p1-65535

Starting Nmap 5.00 ( http://nmap.org ) at 2011-11-09 09:58 PST
NSE: Loaded 0 scripts for scanning.
Warning: Hostname localhost resolves to 2 IPs. Using 127.0.0.1.
Initiating Connect Scan at 09:58
Scanning localhost (127.0.0.1) [65535 ports]
Discovered open port 22/tcp on 127.0.0.1
Connect Scan Timing: About 18.56% done; ETC: 10:01 (0:02:16 remaining)
Connect Scan Timing: About 44.35% done; ETC: 10:00 (0:01:17 remaining)
Completed Connect Scan at 10:00, 112.36s elapsed (65535 total ports)
Host localhost (127.0.0.1) is up (0.00s latency).
Interesting ports on localhost (127.0.0.1):
Not shown: 65533 filtered ports
PORT   STATE  SERVICE
22/tcp open   ssh
80/tcp closed http

Read data files from: /usr/share/nmap
Nmap done: 1 IP address (1 host up) scanned in 112.43 seconds
           Raw packets sent: 0 (0B) | Rcvd: 0 (0B)

I think this shows that 5903 is blocked somehow. Which I pretty much knew. The question remains what is blocking it and how to modify.

Re-re-edit:

To check Paul Lathrop's suggested answer, I first verified my ip address with ifconfig:

eth0      Link encap:Ethernet  HWaddr 02:16:3e:42:28:8f
          inet addr:10.0.10.3  Bcast:10.0.10.255  Mask:255.255.255.0

Then tried to telnet to 5903 from that address:

# telnet 10.0.10.3 5903
Trying 10.0.10.3...
telnet: Unable to connect to remote host: Connection timed out

No luck.

Re-re-re-re-edit:

Ok, I think I have isolated it a bit to vncserver, not the firewall, darn it. I shut off vncserver and had netcat listen on port 5903. My vnc client then was able to establish a connnection and sit and wait for a response. Looks like I should be chasing a vnc problem. At least that is progress Thanks for the help