%META:TOPICPARENT{name="ErrorMessagesU"}%
= Error Message: {{{Unable to create listener (Address already in use)}}} =

"Unable to create listener" errors are returned when some other service is utilizing the Broker's UDP or TCP ports; this may be a previously started instance of the Broker, or any other process. If you receive "Unable to create listener" errors, take the following action: 

# Access the Multi-Tier server components installation.
# Use <b><code><nowiki>ps -ef | grep oplrqb | grep -v grep</nowiki></code></b> (Unix) or the Task Manager (Windows) to search for a running Broker process. If you find one, terminate it. You cannot run two Broker instances on one machine.
# If no Brokers are running, run <b><code><nowiki>netstat -a | grep 60001</nowiki></code></b> from DOS or a UNIX terminal to check whether another service is using UDP Port <b><code>60001</code></b>. If so, try to reassign that service, or start the Broker before the other service.
# If UDP port <b><code>60001</code></b> is free, use <b><code><nowiki>netstat -a | grep &lt;port-number&gt;</nowiki></code></b> to check the status of the Broker's <b><code>Listen</code></b> and <b><code><nop>PortLow</code></b> TCP ports.  These ports both default to <b><code>5000</code></b>. However, you may want to verify your settings. Take the following action:
## Use a text editor to open your <b><code>oplrqb.ini</code></b> file. You will find this file in the <b><code>/bin</code></b> sub-directory of your Multi-Tier server components installation.
## Locate the <b><code>[Protocol TCP]</code></b> section.
## Note the values set for <b><code><nop>PortLow</code></b> and <b><code>Listen</code></b>.
## Search for these port numbers in your <b><code>netstat</code></b> output.


== Related Documentation ==

* [[MTFirewallConfiguration | Firewall Considerations for Multi-Tier "Enterprise" Edition Data Access Drivers]]
* [[ConfigureServer-sideFirewallsForMulti-TierConnectivity | Configuring Server-side Firewalls for Multi-Tier Connectivity]]
* [[UnableContactLicenseManager | Error Message: Unable to contact the OpenLink License Manager]]
* [[OplmgrNetworking | OpenLink License Manager Networking Considerations]]
* [[ConfigureMulti-TierRequestBrokerForUseOnMachinesWithMultipleNetworkCards | Configure Multi-Tier Request Broker for Use on Machines with Multiple Network Cards]]