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

"Unable to create agent listener" errors are returned when all ports allocated for agent use (i.e., all ports between {{{PortLow}}} and {{{PortHigh}}}, as set in the active Rulebook) are in use by other processes (including other agent instances) when the Broker tries to launch a new Agent instance.

If you encounter such errors --

# Access the Multi-Tier server components installation.
# Use a text editor to open your active Rulebook (default, {{{oplrqb.ini}}}). You will generally find this file in the {{{bin}}} sub-directory of your <nop>OpenLink server components installation.
# Locate the {{{[Protocol TCP]}}} section.
# Note the values set for {{{PortLow}}} and {{{PortHigh}}}.  Ensure that this range is at least as large as the maximum number of agent instances you will have running simultaneously.  We generally recommend allocating an additional 10-100 ports to this range, to allow unrelated processes to consume some ports as assigned by the OS.
# Save the Rulebook, restart the Broker, and monitor for recurrence of the error.