> db2 udb V8 instance on Windows is started,  however, the TCP port
> 50000 is not listening, how we troubleshoot this issue?  which log I
> should look into?
> 
> Thanks in advance.

Check that DB2 is configured to use TCPIP for networking:


  C:\>db2set DB2COMM

  TCPIP


Check the SVCENAME DBM configuration parameter with GET DBM CFG:


  C:\>db2 GET DBM CFG | find "SVCENAME"

   TCP/IP Service name                       (SVCENAME) = db2c_DB2


The "db2c_DB2" value refers to a value in the "services" file which on
Windows can be found under %SystemRoot%\system32\drivers\etc:


  C:\>find "db2c_DB2" %SystemRoot%\system32\drivers\etc\services

  ---------- C:\WINDOWS\SYSTEM32\DRIVERS\ETC\SERVICES
  db2c_DB2        50000/tcp


If the above settings are the same on your machine, then DB2 should
indeed be listening on port 50000. If the services file indicates
something other than 50000, simply edit it and restart the instance.

Next thing to check is whether anything is listening on port 50000. For
WinNT, Win2k, and WinXP:


  C:\>netstat -an | find "50000"

    TCP    0.0.0.0:50000          0.0.0.0:0              LISTENING


This should confirm *something* is listening on port 50000. To find out
exactly what it is, use SysInternal's TCPView[1]. If you're on Win2k3
you can find out without the aid of TCPView:


  C:\>netstat -anb | find "50000"

    TCP   0.0.0.0:50000       0.0.0.0:0          LISTENING    3132

  C:\>tasklist | find "3132"

  db2syscs.exe            3132 Console               0   193,964 K


If the task listening on port 50000 isn't db2syscs.exe then something's
getting in DB2's way. You'll need to shift it or DB2 to a different
port (or disable it).

If all the above checks out, check the firewall configuration
(CheckPoint, Symantec, or under Win2k3 the Windows Firewall). Don't
bother trying to check every individual setting initially. Just shut
down the firewall temporarily and attempt to connect to the DB2
instance with a client. If it works, you'll at least know *something*
in the firewall is at fault, so check that db2syscs.exe is allowed to
act as a server or accept connections, and/or that TCP port 50000 is
permitted to accept inbound connections.

If you are still unable to connect to the DB2 server with a client,
it's time to start suspecting the client's configuration. Check the
node configuration on the client has the correct host and port
specified, and that the client's firewall (if it has one) is not
blocking the client from connecting.


[1]
http://www.microsoft.com/technet/sysinternals/Networking/TcpView.mspx