LonMaker reports "Could not listen on POET/TCP: the address specified is already in use (DB #-2523)" whenever I try to open or create a network database. How do you set different TCP Port numbers other than 6001 and 6002 for the POET server? (KB562)

Question Detail

Microsoft Exchange 2003 Server and other OEM software sometimes use TCP ports 6001 or 6002. This causes a conflict since the POET server (FastObjects DB) defaults to TCP ports 6001 and 6002.

Check that the ports used by LNS are not being blocked (firewalled) or used by another application. To verify this, open a command prompt as Administrator (type "cmd" in your search box, then right-click and select Run as Administrator) and type:

netstat -ab >ports.txt

This will create a ports.txt file in your current location containing a list of in-use TCP and UDP ports. Look for an entry saying {your computer name}:6001 or 6002. If you find one, you have located a conflict and you will need to change the POET Port numbers.

Check if you run a firewall on this PC. If yes, you need to find the list of Programs with their Internet Access level and make sure you have given access to the appropriate files. To run LonMaker/LNS , you need to give access to ptserv32.exe, LonMaker.exe, lonpoint.exe, visio.exe, lmwbrw32.exe and lsass.exe.


You can modify the ports used by the POET server and clients by modifying the "Services" file (%WINDIR%\System32\Drivers\Etc\Services) using a text editor like Wordpad.exe or Notepad.exe.

For example, to change the POET port numbers to 7001 and 7002, add/modify the following lines in the "Services" file. The '#' in the example indicates that the following text is a comment.

For Win XP: use "Windows\System32\Drivers\Etc\Services". If you see the "poet" and "_poet" entries, go ahead and change the port numbers from 6001 and 6002 to 7001 and 7002 or 8001 and 8002.


Note, netstat doesn't always show if the ports are in use.  If you still have a problem try a different port pair.

If you don't see these entries, simply add the lines below.

poet             7001/tcp                           #FastObjects services
_poet            7002/tcp                           #FastObjects services

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