Why does my code run 2 different ways with the exact same code? - vb.net

Question

I have an application that I have started developing that monitors websocket messages from all clients connected to the websocket server by relaying all messages received from the server to this application.
Problem
When I run my program (In visual studio I hit Start), it builds and starts up perfectly, and does most of the functionality the same everytime. However, I have a common occurance of a portion of code that will not run the same. Below is the small snippet of that code.
msg = "set name monitor"
SendMessage2(socket, msg, msg.Length)
msg = "set monitor 1"
SendMessage2(socket, msg, msg.Length)
Console.WriteLine("We are after our second SendMessage2 function")
I know that the two calls to SendMessage2 are always executed because visual studio's debug console will output the following
We are at the end of the SendMessage2 Sub
We are at the end of the SendMessage2 Sub
We are after our second SendMessage2 function
I also know when it executes correctly because my websocket server will either output one of the two blocks
Output when app runs correctly
Client 4 connected
New thread created
Connection received. Parsing headers.
Message from socket #4: "set name monitor"
Message from socket #4: "set monitor 1"
Output when app runs incorrectly
Client 4 connected
New thread created
Connection received. Parsing headers.
Message from socket #4: "set name monitor"
Notice how the second output is missing the second message from the monitor application.
What have I tried
Using a string variable to call the functions
Calling the functions using static string arguments (not using the variable msg)
SyncLocking the functions separately
SyncLocking inside the SendMessage2 function
Reordering the functions (swapping the strings to change behavior)
TL;DR
Why is it that even when I do not change my code, my program will execute two separate ways? Am I doing something incorrectly when calling my SendMessage2 Sub?
I am all out of ideas. I am willing to try any recommendation to fix this problem.
All code can be found on GitHub here

Answer 1

So I figured it out.
It is actually not the VB application that is messing up. Nor was my server. While debugging I was looking at the number of bytes received by my server and I noticed the following:
Client 4 connected
New thread created
Connection received. Parsing headers.
bytes read: 25
Message from socket #4: "set name monitor"
bytes read: 22
Message from socket #4: "set monitor 1"
Ok great we have 25 bytes from set name monitor and 22 bytes from set monitor 1
Client 4 connected
New thread created
Connection received. Parsing headers.
bytes read: 47
Message from socket #4: "set name monitor"
And boom. Both programs were doing their jobs, sending the correct number of bytes every time and reading the correct number. However, the VB application is sending them so quickly back to back that my server was reading all 47 bytes at a time instead of the separate 25 and 22 bytes.
Solution
I solved this problem by implementing a secondary buffer in my server to store off all bytes after the first message should multiple messages by group like this. Now I check if my secondaryBuffer is empty before reading in new bytes.
Here is a portion of the code used to solve the problem
/*Byte Check*/
for (j=0; j < bytes; j++) {
if (j == 0)
continue;
if (readBuffer[j] == '\x81' && readBuffer[j-1] == '\x00' && readBuffer[j-2] == '\x00') {
secondaryBytes = bytes - j;
printf("Potential second message attached to this message\nCopying it to the secondary buffer.\n");
memcpy(secondaryBuffer, readBuffer + j, secondaryBytes);
break;
}//END IF
}//END FOR LOOP
/**/