Error

[BridgingDragon]

Whenever I'm AFK and I come back to my computer there's this error in the console.

Unhandled Exception:
System.IO.InvalidDataException: Failed to process incoming packet of type ChatMessage. (PacketID: 15, Protocol: 757, LoginPhase: False, InnerException: System.FormatException). ---> System.FormatException: Input string was not in a correct format.
  at System.Text.StringBuilder.AppendFormatHelper (System.IFormatProvider provider, System.String format, System.ParamsArray args) [0x00060] in <533173d24dae460899d2b10975534bb0>:0 
  at System.String.FormatHelper (System.IFormatProvider provider, System.String format, System.ParamsArray args) [0x00023] in <533173d24dae460899d2b10975534bb0>:0 
  at System.String.Format (System.String format, System.Object[] args) [0x00020] in <533173d24dae460899d2b10975534bb0>:0 
  at MinecraftClient.Logger.LoggerBase.Chat (System.String msg, System.Object[] args) [0x00000] in <e6eefcb96afd4423b99f6ba2d17e239c>:0 
  at MinecraftClient.McClient.OnTextReceived (System.String text, System.Boolean isJson) [0x00084] in <e6eefcb96afd4423b99f6ba2d17e239c>:0 
  at MinecraftClient.Protocol.Handlers.Protocol18Handler.HandlePacket (System.Int32 packetID, System.Collections.Generic.Queue`1[T] packetData) [0x00574] in <e6eefcb96afd4423b99f6ba2d17e239c>:0 
   --- End of inner exception stack trace ---
  at MinecraftClient.Protocol.Handlers.Protocol18Handler.HandlePacket (System.Int32 packetID, System.Collections.Generic.Queue`1[T] packetData) [0x0276c] in <e6eefcb96afd4423b99f6ba2d17e239c>:0 
  at MinecraftClient.Protocol.Handlers.Protocol18Handler.Update () [0x00036] in <e6eefcb96afd4423b99f6ba2d17e239c>:0 
  at MinecraftClient.Protocol.Handlers.Protocol18Handler.Updater () [0x00010] in <e6eefcb96afd4423b99f6ba2d17e239c>:0 
  at System.Threading.ThreadHelper.ThreadStart_Context (System.Object state) [0x00014] in <533173d24dae460899d2b10975534bb0>:0 
  at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, System.Object state, System.Boolean preserveSyncCtx) [0x00071] in <533173d24dae460899d2b10975534bb0>:0 
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, System.Object state, System.Boolean preserveSyncCtx) [0x00000] in <533173d24dae460899d2b10975534bb0>:0 
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, System.Object state) [0x0002b] in <533173d24dae460899d2b10975534bb0>:0 
  at System.Threading.ThreadHelper.ThreadStart () [0x00008] in <533173d24dae460899d2b10975534bb0>:0 
[ERROR] FATAL UNHANDLED EXCEPTION: System.IO.InvalidDataException: Failed to process incoming packet of type ChatMessage. (PacketID: 15, Protocol: 757, LoginPhase: False, InnerException: System.FormatException). ---> System.FormatException: Input string was not in a correct format.
  at System.Text.StringBuilder.AppendFormatHelper (System.IFormatProvider provider, System.String format, System.ParamsArray args) [0x00060] in <533173d24dae460899d2b10975534bb0>:0 
  at System.String.FormatHelper (System.IFormatProvider provider, System.String format, System.ParamsArray args) [0x00023] in <533173d24dae460899d2b10975534bb0>:0 
  at System.String.Format (System.String format, System.Object[] args) [0x00020] in <533173d24dae460899d2b10975534bb0>:0 
  at MinecraftClient.Logger.LoggerBase.Chat (System.String msg, System.Object[] args) [0x00000] in <e6eefcb96afd4423b99f6ba2d17e239c>:0 
  at MinecraftClient.McClient.OnTextReceived (System.String text, System.Boolean isJson) [0x00084] in <e6eefcb96afd4423b99f6ba2d17e239c>:0 
  at MinecraftClient.Protocol.Handlers.Protocol18Handler.HandlePacket (System.Int32 packetID, System.Collections.Generic.Queue`1[T] packetData) [0x00574] in <e6eefcb96afd4423b99f6ba2d17e239c>:0 
   --- End of inner exception stack trace ---
  at MinecraftClient.Protocol.Handlers.Protocol18Handler.HandlePacket (System.Int32 packetID, System.Collections.Generic.Queue`1[T] packetData) [0x0276c] in <e6eefcb96afd4423b99f6ba2d17e239c>:0 
  at MinecraftClient.Protocol.Handlers.Protocol18Handler.Update () [0x00036] in <e6eefcb96afd4423b99f6ba2d17e239c>:0 
  at MinecraftClient.Protocol.Handlers.Protocol18Handler.Updater () [0x00010] in <e6eefcb96afd4423b99f6ba2d17e239c>:0 
  at System.Threading.ThreadHelper.ThreadStart_Context (System.Object state) [0x00014] in <533173d24dae460899d2b10975534bb0>:0 
  at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, System.Object state, System.Boolean preserveSyncCtx) [0x00071] in <533173d24dae460899d2b10975534bb0>:0 
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, System.Object state, System.Boolean preserveSyncCtx) [0x00000] in <533173d24dae460899d2b10975534bb0>:0 
  at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, System.Object state) [0x0002b] in <533173d24dae460899d2b10975534bb0>:0 
  at System.Threading.ThreadHelper.ThreadStart () [0x00008] in <533173d24dae460899d2b10975534bb0>:0 

and then it crashes.

[ORelio]

I'm not 100% sure of the root cause but I think the error happens here:

Minecraft-Console-Client/MinecraftClient/McClient.cs

Line 1963 in 76a10c0

Log.Chat(Translations.Get("mcc.link", link), false);

Try setting showchatlinks=false in config file?

[ReinforceZwei]

I'm able to reproduce the problem with the following example code:
Online C# playground SharpLab

var content = "http://example.com/{abc}/ok";
var toBeFormat = "Link: {0}";
var format = string.Format(content, toBeFormat);
Console.WriteLine(format);

If the link contains { or }, string.Format will throw an FormatException.

---

Maybe someone is trying Log4Shell?

Edit: My example code is wrong

[ORelio]

Good catch! We should automatically escape this in the Log class 👍

[ReinforceZwei]

I've noticed that calling to Log.Chat() method has an false parameter after, which will cause Log.Chat() method to format the string again.

Minecraft-Console-Client/MinecraftClient/Logger/LoggerBase.cs

Lines 26 to 29 in 76a10c0

	public void Chat(string msg, params object[] args)
	{
	Chat(string.Format(msg, args));
	}

Formatting the string will then cause the crash if the string contains { or }.

What is that false parameter for? If it has no usage, we can remove it and fix the crash issue.

[ORelio]

Good catch, after diffing a bit, the bug was likely introduced in 38a890f (link to diff in commit):

            if (Settings.DisplayChatLinks)
                foreach (string link in links)
-                    ConsoleIO.WriteLogLine(Translations.Get("mcc.link", link), false);
+                    Log.Chat(Translations.Get("mcc.link", link), false);

The false argument was intended for ConsoleIO.WriteLogLine:

Minecraft-Console-Client/MinecraftClient/ConsoleIO.cs

Lines 392 to 402 in a018304

	/// <summary>
	/// Write a prefixed log line. Prefix is set in LogPrefix.
	/// </summary>
	/// <param name="text">Text of the log line</param>
	/// <param name="acceptnewlines">Allow line breaks</param>
	public static void WriteLogLine(string text, bool acceptnewlines = true)
	{
	if (!acceptnewlines)
	text = text.Replace('\n', ' ');
	WriteLineFormatted(LogPrefix + text);
	}

But it has no use for Log.Chat and should indeed be removed.

[ReinforceZwei]

This issue should be fixed in 2524802.