When using send() to send data from a text file from client to server through TCP stream, how do I send all the data but only 4 bytes at a time?

Below is an excerpt from my client.cpp file:

//Variables previously declared
char buffer[1024];
char sendbuffer[100];
int sockfd, b;

//Opens specified file
FILE *fp = fopen(argv[3], "rb"); 

while( (b = fread(sendbuffer, 1, sizeof(sendbuffer), fp)) > 0 ) 
{
    send(sockfd, sendbuffer, b, 0);
}

I am new to client-server programming, and I'm far from being extremely proficient in C++.

When I use the code above, it's successful sending the inf, but it obviously isn't going to send the data 4 bytes at a time.

If I modified the line containing send() as shown below without making other necessary changes, I'm certain that it would be incorrect.

send(sockfd, sendbuffer, 4, 0);

It's also a pain to debug because when I make a change to the code, I have to continuously simulate a client-server interaction, which takes time to set up.

What would be the most efficient way to send this text file data 4 bytes at a time?

Also, can anyone suggest a tool or method for quickly debugging client-server programs?

Let me know if more information is needed. Thanks