Bug still present in 2024 (ue version 5.4.1), lol, seems part of greater problem with server-client communication in editor.
Dedicated server and client has multiple problems in editor.
Basicly, y still will be kicked out in pie if you connect to server.
Join session not in pie but standalone or open level, open command, result to “do nothing” if connect from client side. Works normaly only in packed version.
The only way to test server-client now if y have login (lobby) menu seems go to
Advanced settings->launch separate server
Net mode->play as standalone
You will be still kicked out from server first time, failed to join host, but second try will result you to connect it eventually.
Before doing this y need to force server to change login/lobby menu map in blueprients (another bug) on begin play for example. (details below)
or
Net mode->play as client
launch standalone
and open level on server itself (like 127.0.0.1:17777).
play as client still result to join server session right after start (it’s intended behaviour i guess?), but there is no tick in advanced settings to disable initial connection now and cause of bug below no correct map travel.
Also seems there is another bug: server default map doesn’t work in editor, found out experimental way during tests, it basicly opens editor map when you launch it on server (our login/lobby map), not server map itself.
Peoples tried to bypass this bug in code to force travel, but seems this workaround doesn’t work too. UGameInstance::ClientTravelToSession
You need to call GameSession on client and use player controller with id 0 with this function after server launches, but it always returns false.