C# Wpf socket chat programs - wpf

Question

enter image description here I am creating a chat program in the wpf environment. If I type in English, the font doesn't break, but if I type in letters other than English, it breaks
Why is it breaking?
Where you converted the message
public string ReadMessage()
{
byte[] msgBuffer;
var length = ReadInt32();
msgBuffer = new byte[length];
_ns.Read(msgBuffer, 0, length);
var msg = Encoding.Default.GetString(msgBuffer);
return msg;
}
So I gave a value of 1024 to the length, and the text didn't break,
but why it didn't break when I put the value of 1024
And when the value 1024 is given, the text appears on the console,
but only username appears on the mainwindow screen, and can't see the message I sent
Where to Show Converted Messages
public Client(TcpClient client)
{
ClientSocket = client;
UID = Guid.NewGuid();
_packetReader = new PacketReader(ClientSocket.GetStream());
var opcode = _packetReader.ReadByte();
Username = _packetReader.ReadMessage();
Console.WriteLine($"[{DateTime.Now}]: Client {Username} sucess to acess:");
Task.Run(() => Process());
}
void Process()
{
while (true)
{
try
{
var opcode = _packetReader.ReadByte();
switch (opcode)
{
case 5:
var msg = _packetReader.ReadMessage();
Console.WriteLine($"[{DateTime.Now}]: from {Username} {msg}");
Program.BroadcastMessage($"[{DateTime.Now}]:{Username} {msg}");
break;
default:
break;
}
}