fpsockets does not work in fpc-trunk
the packages/fcl-net/tests/tfpsock2.pp report error: 10047, send to call failed, SendStrTo(...)
People say it works in the trunk version few months ago. But it does work in the trunk version 2 days ago.
Also see https://forum.lazarus.freepascal.org/index.php/topic,72989.0.html