Right you are Angus.

I suspect that changing between port 7771 and 7772 is ok at the moment because they both have the same search parameter in the first line of the file "10000000000:M:1:2:258"

Where you would have a problem is with switching to or from port 7773 bacause the search parameter is different "10000000000000:M:1:2:258", having 3 additional zeros in the depth.

That difference could cause a number of rejections until the client sorts itself out.

If you want to be completely sure about the switch between ports, stop the client, then delete the "workfile.txt" file and any "zXXXXXXX" files in the client folder (those are work-in-progress files which the client can pick up again and cause the same issue). Any pairs left in those files will get handed out to another participant as soon as they expire (currently all 3 ports have a jobMaxTime of 1 day - that is the expiry time). Change your port number and fire up the client. It will automatically create a new work file from the new port with the search parameter from that port.

You can observe the jobMaxTime and other parameters on the port report page:
http://primesearch.free-dc.org/stats...p?content=port
which now includes the server status report:
http://primesearch.free-dc.org/stats...rver_status_ib