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DB2 Not Listening on Port 50000?

· 3 min read
Sławomir Cichy
Sławomir Cichy
Backend Engineer @ Sci Software

DB2 Not Listening on Port 50000? Check This Before You Make Any Changes!

After installing DB2, you might find that your instance isn't listening on the default TCP/IP port (50000). This often leads to remote connection and authentication issues. Before you start changing your configuration, you need to understand why this might be happening. The problem is often not a lack of configuration, but an unexpected value.

Find the Port DB2 Is Actually Listening On​

The default port is one thing, but the actual configuration is another. Your DB2 instance may have been configured to use a custom port during installation.

Use the following commands to diagnose the issue.

Step 1: Check the communication protocol​

First, ensure that DB2 has TCP/IP communication enabled at all.

db2set DB2COMM

If the response is TCPIP, the protocol is active. If not, set it: db2set DB2COMM=TCPIP.

Step 2: Check the service name​

Now, you need to check which port or service name DB2 has assigned for listening.

db2 get dbm cfg | grep SVCENAME

Ideally, the result is (SVCENAME) = 50000. However, you'll often see a service name, such as (SVCENAME) = db2c_db2inst1. This means the port isn't defined numerically, but by a name.

Step 3: Verify the port in the operating system​

If db2 get dbm cfg returned a service name, you must check which port that name maps to in the operating system. The /etc/services file contains these mappings.

cat /etc/services | grep db2c_db2inst1

Here, you might discover that DB2 is listening on a completely different port, for instance, db2c_db2inst1 25010/tcp. This is the key to solving your problem: DB2 wasn't broken - it was simply configured to listen on port 25010 instead of 50000.

Solution: Adjust the Configuration to Your Needs​

Now that you know which port DB2 is listening on, you have two options:

  1. Use the custom port (25010): If the custom port is acceptable, simply instruct your applications to connect on port 25010 instead of 50000.
  2. Change the port to the default (50000): If you prefer to use the standard port, update the DB2 configuration.

Changing the port to the default 50000​

This is a simple and quick operation.

# Stop the instance
db2stop

# Update the listening port
db2 update dbm cfg using SVCENAME 50000

# Start the instance again
db2start

# Check if it's listening on port 50000
netstat -lnptu | grep 50000

If all went as planned, the netstat command should now show the db2sysc process listening on port 50000. Just remember to also open this port in your firewall!

Summary: Before you change a configuration, always diagnose the existing state first. The solution to a problem often lies in understanding why a system is behaving a certain way. In this case, DB2 wasn't broken—it was just listening on a different port.