C# - Matrix Printing Incorrectly on a Separate Thread - multithreading

Question

I'm currently making a Console Application game, and am working on the multiplayer version.
When I am receiving packets, I create a new thread to handle the packets, in order to return to the ReceiveFrom command as soon as possible.
The newly created thread should reprint the whole Matrix, using the new information it got regarding the changes in the matrix (it should print the Matrix with updated player positions).
The problem is, when the Print method is called on the new thread, it is badly performed. It prints the matrix very inaccurately, and many characters of the matrix are just in a mess on the Console Screen.
Here are the methods:
void Receive()
{
while (true)
{
byte[] msg = new byte[1024];
client.Receive(msg);
Thread handle = new Thread(() => HandleInput(msg));
handle.Start();
}
}
void HandleInput(byte[] msgX)
{
string data = Encoding.ASCII.GetString(msgX);
data = data.Replace("\0", "");
if (data.Contains('*') || data.Contains('\0') || data.Contains(' ')) // Move Packet (moving objects in a matrice)
{
// for example, a move packet can be: '*'!12!10
char ToMove = char.Parse(data.Split('!')[0]);
int X = int.Parse(data.Split('!')[1]);
int Y = int.Parse(data.Split('!')[2]);
grid[X, Y] = ToMove;
Print();
}
}
void Print() // print a 20x50 matrix
{
Console.Clear();
for (int y = 0; y < 52; y++)
{
Console.Write('-');
}
Console.WriteLine();
for (int i = 0; i < 20; i++)
{
Console.Write('|');
for (int j = 0; j < 50; j++)
{
Console.Write(grid[i,j]);
}
Console.WriteLine('|');
}
for (int x = 0; x < 52; x++)
{
Console.Write('-');
}
}
But, when I tried to treat the input and print the matrix on the same thread of the Receive method, it worked fine. The problem printing it only came when I printed the matrix on a separate thread.
So why does this happen? Why can't a separate thread just print the matrix correctly?

Answer 1

You create a new thread for every received kilobyte, but those threads are not guaranteed to start running in sequence, to wait one another, nor to finish running in sequence.
There is also no guarantee that network client will receive all needed bytes in one call of Receive method. It may happen in one, but it may happen in several calls. It may also happen that two Send methods from the other side of the connection are merged into one message. All that is guaranteed in network communication is the ordering of the bytes in the stream, and nothing else.
Your next question will probably be "so how do I make it work"? I can't do the job for you, but this is in general how I would do it:
Read chunk of bytes from the stream and store it in some buffer.
Check in the loop for existence of a complete message in the buffer. If there is such a message remove that message from the buffer, and process the message. I would process it in the same thread, and only if there are problems with that approach I would consider additional threads (or rather just one additional thread to whom I would be sending all the messages).
Repeat the loop until all complete messages are removed from the buffer, and continue reading the stream.