= doc.FAQ.CannotStartBroker

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 [[OpenLink]]  's Request Brokers are listening services. [[OpenLink]]  's 4.x and newer Brokers listen on the TCP port that is passed to the Listen parameter. The Listen parameter appears in the Protocol TCP section of the Session Rules Book. [[OpenLink]]  's 3.x and 1.x Brokers listen on [[PortLow]]  . [[PortLow]]  appears in the Protocol TCP section of the Session Rules Book. [[OpenLink]]  's Request Brokers also use UDP port 60001 to broadcast license information. 

Use the following guidelines to troubleshoot Broker startup issues: 

*Ensure that [[OpenLink]]  's Request Broker is installed.  
*Ensure that Unix Request Brokers are executable.  
*Run oplrqb -? from the /bin sub-directory of the [[OpenLink]]  server components installation. Ensure that the Request Broker returns version and usage information. Troubleshoot errors, as required.  
*Run uname -a on Unix servers. Compare the Broker's platform of compilation with the platform identified with uname -a. Ensure that the platform of compilation is compatible with the platform returned by uname -a. Install more suitable builds, as appropriate.  
*Open the Session Rules Book and identify the Broker listening port.  
*Run netstat -an, or an equivalent network utility, to check for existing activity on the Broker's listening port. Reassign a free port, or wait for previous listeners to be cleared (up to 2 minutes) as required.  
*Obtain operating system patch information. Some patches may interfere with the Broker's ability to run.  

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