Thread: Winsock recv problems

Hi all,

First off I apologize if this is in the wrong forum. I know its a networking question but its specifically for windows.

I have coded my server to send the string "hello world\r\n\r\n"

My client attempts to read the string like so

Code:

void response(void)
	{
	char String[20] = "1234567890123456789";
	    int RetVal = SOCKET_ERROR;
		
		while (RetVal == SOCKET_ERROR)
		{
			RetVal = recv(Socket, String, strlen(String), 0);
		}

		cout << String << endl;
	}

Now when I call the "response" function it outputs the first character from the "hello world" string which is obviously a 'h' followed by 19 junk values. If I the call the "response" function again it manages to output "elloWorld".

Any idea why this is happening?

Thanks

Edit: Is there anyway that I can code it so instead of reading everything thats been sent in one go, can I loop through and read one character at a time until say the character '\r' is read? Thanks

> Any idea why this is happening?
The network does NOT guarantee that if you send "hello world" in ONE send() call that you will receive "hello world" in a single recv() call.

Message fragmentation and reassembly is a problem you need to address yourself when using a TCP connection, since it is a streaming protocol.

Contrast that with UDP which is a packet oriented protocol (and an unreliable one at that). Either you get the whole packet, or none of the packet.

> can I loop through and read one character at a time until say the character '\r' is read?
Yes you can do that if you want.
Wrap it up in a function called recvAWholeLikeLikeFgets() perhaps, so you don't have to keep doing it over and over.