The C$SOCKET function to create a client connection sometimes fails using extend 10.x.x whereas it appears to be working in previous versions.
The C$SOCKET function to create a client connection has always assumed that the server name passed is filled with LOW-VALUES on the right, though this was never documented. As a result, sometimes this function would work correctly, and occasionally it would fail.
If you right-fill the server-name variable with LOW-VALUES, this will always work.
Starting with version 10.2, this will no longer be required.