Windows C socket, read N bytes from the socket stream

Question

How do i read exactly N bytes from the socket stream in C on windows 10, the only function i was able to find is recv() that reads everything.

Answer 1

As the official documentation says , you have to pass to the recv() function 4 parameters:

• s - The socket descriptor
• buf - The memory buffer which will hold the read data
• len - The length of the memory buffer
• flags - "A flag or a set of flags that influence the behavior of this function"

In particular, when the last parameter is set to the defined value MSG_WAITALL , the recv() function will complete only when one of these events occurs:

• The buffer supplied by the caller is completely full.
• The connection has been closed.
• The request has been canceled or an error occurred.

In other words, if you want to read exactly 10 bytes, you should create a 10 bytes buffer and ask the recv() function to return only once the buffer is full!

char data[10];
recv(streamSocket, data, 10, MSG_WAITALL);

Hope it helps