Checking if buffer is completely empty...

Hey guys. I figured out a way to organize the UI for the ECS program I am working on. After I recv() the message from the socket into buff, I could check if it received any message(if the buffer is not completely empty). if it id, then decrypt the message and then show it to the user. But if the buffer is empty, then don't print anything at all on the screen. Because right now, if the message is empty, it still prints "Message from client: " without the message

here is the code:

Code:

---

                if(frkserv > 0)
                {
                    if(recv(clisock, &buff, sizeof(buff), 0) != NULL)
                    {
                        if(buff != ' ')
                        {
                            ecsdecrypto(buff);
                            printf("Message from client: %s\n", buff);
                        }
                    }           
                }

---

Just part of the code that I am talking about. I need to replace if(buff != ' ') with another condition. I need to check if there is anything in the buffer. I could do it with a loop through all the elements of the char[] and check, but I thought there was a function to do it.

Maybe by checking the proper return result of recv(), which does NOT return a pointer.

If it's non-blocking, you should be expecting a return result of zero, AND errno set to EAGAIN.
Meaning, nothing at the moment (=0), and try again later.

I knew recv() would wait until it a message was available on a socket. That's why i was gonna check the string instead of the recv.

either strcmp() or loop through the string. I don't think there's another way.
And I'd prefer the latter one, if you want to filter strings like " ", " ", etc.

If the socket is blocking, there's no such thing as a completely empty buffer. You're always going to get at least 1 char.

What you might have is a not completely filled buffer, but that's something you need to deal with yourself.

Thanks. I just did if(recv(clisock, &buff, sizeof(buff), 0) != 0 && recv(clisock, &buff, sizeof(buff), 0) != 0)


Thank you very much salem.

That works?

Yes. Thank You! Now, all I have trouble with is the prompt to send a new message to the server. I gotta find a way to fix it. If I have any major trouble. I will ask for help in this thread! It's related!

I doubt this works. This will read two messages and discard the first one. Later on, this will definitely lead to unwanted behaviour