"TNS-12535: TNS:operation timed out" error after listener restart

Question

I have two related questions:
Scenario 1:
1. I have two remote Windows machines with database on each. One is Win 2003 Server (machine A) and another one is Win XP (machine B)
2. I can ping from A to B.
3. I can ping from B to A.
4. I can tnsping from A to B.
5. I CAN'T tnsping from B to A.
6. Windows Firewall on both machines are off.
What could be possible reason for point# 5?
Scenario 2:
Now, the second part:
1. I had an unwanted entry in tnsnames.ora on B which I removed.
2. Then I restarted the listener on B. Actually, I wanted to restart the one on A to check if that resolves issue mentioned in point# 5 above.
3. I tried tnsping from A to B but suprisingly it is also giving "operation timed out" error now. So now tnsping not working from either sides.
I didn't make any changes in listener.ora on B, just stopped it and started again. Only change made was removing unwanted entry in tnsnames.ora on B.
Why does that affected database connectivity from A to B which was working fine previously?
If any extra information needed please let me know, and thanks in advance for your answers.
- Ramesh

Answer 1

DB names on both machines: ORCL
listener.ora on B (Win XP) - This was working before listener restart, I mean, I was able to connect to DB on B from A.
# listener.ora Network Configuration File: C:\app\Test\product\11.2.0\dbhome_1\NETWORK\ADMIN\listener.ora
# Generated by Oracle configuration tools.
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = CLRExtProc)
(ORACLE_HOME = C:\app\Test\product\11.2.0\dbhome_1)
(PROGRAM = extproc)
(ENVS = "EXTPROC_DLLS=ONLY:C:\app\Test\product\11.2.0\dbhome_1\bin\oraclr11.dll")
(SID_DESC =
(GLOBAL_DBNAME = ORCL)
(ORACLE_HOME = c:\app\Test\product\11.2.0\dbhome_1)
(SID_NAME = ORCL)
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = testpc)(PORT = 1521))
ADR_BASE_LISTENER = C:\app\Test
listener.ora on A (Win 2003 Server) - Never able to connect to DB on this machine from A.
# listener.ora Network Configuration File: D:\app\Administrator\product\11.2.0\dbhome_1\NETWORK\ADMIN\listener.ora
# Generated by Oracle configuration tools.
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = CLRExtProc)
(ORACLE_HOME = D:\app\Administrator\product\11.2.0\dbhome_1)
(PROGRAM = extproc)
(ENVS = "EXTPROC_DLLS=ONLY:D:\app\Administrator\product\11.2.0\dbhome_1\bin\oraclr11.dll")
(SID_DESC =
(GLOBAL_DBNAME = ORCL)
(ORACLE_HOME = D:\app\Administrator\product\11.2.0\dbhome_1)
(SID_NAME = ORCL)
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = NRDBSVR.delldomain1.netreachasia.com)(PORT = 1521))
ADR_BASE_LISTENER = D:\app\Administrator
NOTE:
Machine A = NRDBSVR.delldomain1.netreachasia.com (Win 2003 Server)
Machine B = testpc (Win XP)