src/de/steamwar/bungeecore/listeners/mods/Forge.java

@@ -101,13 +101,18 @@ public class Forge extends BasicListener {
             }
 
             //for more information see https://wiki.vg/Minecraft_Forge_Handshake#FML2_protocol_.281.13_-_Current.29
-            Utils.VarInt length = Utils.readVarInt(data, 0);
-            assert length.length + length.value == data.length;
+            Utils.VarInt channelLength = Utils.readVarInt(data, 0);
+            int pos = channelLength.length;
+            assert new String(data, pos, channelLength.value).equals("fml:handshake");
 
-            Utils.VarInt packetId = Utils.readVarInt(data, length.length);
+            Utils.VarInt length = Utils.readVarInt(data, pos);
+            pos += length.length;
+            assert channelLength.length + channelLength.value + length.length + length.value == data.length;
+
+            Utils.VarInt packetId = Utils.readVarInt(data, pos);
+            pos += packetId.length;
             assert packetId.value == 2;
 
-            int pos = length.length + packetId.length;
             Utils.VarInt modCount = Utils.readVarInt(data, pos);
             pos += modCount.length;