From 93f2d7335d69d86c195967b4ff810bea68578d05 Mon Sep 17 00:00:00 2001 From: MrTheShy <49885496+MrTheShy@users.noreply.github.com> Date: Mon, 9 Mar 2026 11:20:53 +0100 Subject: [PATCH] Fix split-screen join failing when connecting to a remote host via UI When a non-host client connected to a remote server through the in-game UI (as opposed to the -ip/-port command line flags), the global variables g_Win64MultiplayerIP and g_Win64MultiplayerPort were never updated from their defaults ("127.0.0.1" and the default port). JoinSplitScreen() relies on these globals to open a second TCP connection for the local split-screen pad, so it would always attempt to connect to localhost, failing immediately on any remote session. Fix: update g_Win64MultiplayerIP and g_Win64MultiplayerPort inside JoinGame() once the primary connection is established. This ensures subsequent JoinSplitScreen() calls always reach the correct host regardless of how the session was joined. Additionally, guard PushFreeSmallId() against recycling smallIds in the range [0, XUSER_MAX_COUNT), which are permanently reserved for the host's local controller slots. Previously, if a host-side local pad disconnected its smallId could re-enter the free pool and be handed to an incoming remote client, causing that client's IQNetPlayer slot to collide with a local pad slot on the non-host machine. --- Minecraft.Client/Windows64/Network/WinsockNetLayer.cpp | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/Minecraft.Client/Windows64/Network/WinsockNetLayer.cpp b/Minecraft.Client/Windows64/Network/WinsockNetLayer.cpp index e82118cd0..8c7ff2b4c 100644 --- a/Minecraft.Client/Windows64/Network/WinsockNetLayer.cpp +++ b/Minecraft.Client/Windows64/Network/WinsockNetLayer.cpp @@ -392,6 +392,11 @@ bool WinsockNetLayer::JoinGame(const char* ip, int port) } s_localSmallId = assignedSmallId; + // Save the host IP and port so JoinSplitScreen can connect to the same host + // regardless of how the connection was initiated (UI vs command line). + strncpy_s(g_Win64MultiplayerIP, sizeof(g_Win64MultiplayerIP), ip, _TRUNCATE); + g_Win64MultiplayerPort = port; + app.DebugPrintf("Win64 LAN: Connected to %s:%d, assigned smallId=%d\n", ip, port, s_localSmallId); s_active = true; @@ -733,6 +738,11 @@ bool WinsockNetLayer::PopDisconnectedSmallId(BYTE* outSmallId) void WinsockNetLayer::PushFreeSmallId(BYTE smallId) { + // SmallIds 0..(XUSER_MAX_COUNT-1) are permanently reserved for the host's + // local pads and must never be recycled to remote clients. + if (smallId < (BYTE)XUSER_MAX_COUNT) + return; + EnterCriticalSection(&s_freeSmallIdLock); // Guard against double-recycle: the reconnect path (queueSmallIdForRecycle) and // the DoWork disconnect path can both push the same smallId. If we allow duplicates,