[Version 1.18.2, SOLVED] Running a dedicated server with client(s) on the same computer

[LeeCrafts]

Hello,

I have tried to test my mod on a dedicated server. On one terminal window, I run "./gradlew runServer". The server runs successfully. Now on another terminal window, I run "./gradlew runClient". In that client, I go to "Direct Connection" and enter localhost. However, I am unable to join my own dedicated server; it just says "Failed to log in: Invalid session." In the terminal window running the server, this message gets printed out every time I try to join through a client:

[11:54:02] [Netty Server IO #1/DEBUG] [ne.mi.ne.HandshakeHandler/FMLHANDSHAKE]: Starting new modded impl connection. Found 18 messages to dispatch.
[11:54:03] [Server thread/INFO] [minecraft/ServerLoginPacketListenerImpl]: com.mojang.authlib.GameProfile@48ce4fbf[id=<null>,name=Dev,properties={},legacy=false] (/127.0.0.1:58640) lost connection: Disconnected

Meawhile, the client terminal window just prints out:

[11:54:43] [Render thread/INFO] [minecraft/ConnectScreen]: Connecting to localhost, 25565
[11:54:43] [Netty Client IO #4/DEBUG] [ne.mi.ne.HandshakeHandler/FMLHANDSHAKE]: Starting new vanilla impl connection.

What could possibly be causing this? Is this even how you test your mod on a server?

Edited May 13, 2022 by LeeCrafts

[LeeCrafts]

Thank you. I just had to go to my run directory and edit server.properties so that online-mode = false.

Edit: I tried having more than 1 client on the server (i.e. doing runClient on multiple terminal windows), but it did not work because I "logged in from another location." So I just used my normal Minecraft account to join, and I now have 2 players on my server :)))). I just have to install my custom mod in the launcher I use.

Edited May 13, 2022 by LeeCrafts