TCP Server with select() function

Hi.

last night i tried to write a simple tcp server on select model in C for windows machine but there are some problems.

Here is the code:

Code:

#include <stdio.h>
#include <WinSock2.h>
#include <time.h>



main()
{
	WSADATA			wsadata;

	SOCKET			ListeningSocket;
	SOCKET			NewSocket;

	SOCKADDR_IN		ServerAddr;
	SOCKADDR_IN		ClientAddr;

	FD_SET			fdread;

	struct timeval	time;

	int				port = 4444;
	int				size;
	int				SelectResults;

	char			RcvBuff[200];

	// Initialize Winsock version 2.2

		WSAStartup(MAKEWORD(2,2),&wsadata);

	// Initialize Socket

		ListeningSocket = socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);

	// Initialize Server's SOCKADDR struct

		ServerAddr.sin_family = AF_INET;
		ServerAddr.sin_port = htons(port);
		ServerAddr.sin_addr.s_addr = htonl(INADDR_ANY);

	// Bind Socket with SOCKADDR struct.

		bind(ListeningSocket,(SOCKADDR *)&ServerAddr,sizeof(ServerAddr));

	// Make socket Listening.

		listen(ListeningSocket,5);

	// Accept connection

		size = sizeof(struct sockaddr);
		NewSocket = accept(ListeningSocket,(SOCKADDR *)&ClientAddr,&size);

		while(1)
		{

			// Initialize FD_SETS for the select function.

				FD_ZERO(&fdread); // Clear the fd_set before select.

				FD_SET(NewSocket,&fdread); // Assign Our Socket with fdread set.

			// Seting up timer

				time.tv_sec = 2;	// seconds
				time.tv_usec = 5000; // miliseconds

			// Select function.

				SelectResults = select(0, &fdread, NULL, NULL, &time);

			// Checking select's results.

				if(SelectResults == SOCKET_ERROR)
				{
					printf("Hey man we have a problem with select\n");
					break;
				}

				if(SelectResults > 0)
				{
					// That means we have some readable sockets.
					// Checking if our socket (NewSocket) exists in fdread SET.

					if(FD_ISSET(NewSocket,&fdread))
					{
						printf("Our socket exists and here is what it wants to say:\n\n");

						// Recieving data from socket

						memset(&RcvBuff,0,sizeof(&RcvBuff));
						recv(NewSocket,RcvBuff,200,0);

						printf("%s\n", RcvBuff);

					}

				}

		}
				
}

The first problem is that i can not connect a second client on the server.
The second one is that if client send this: "hat" (three letters) everything goes right but if the client send "hato" (four letters) the server prints out :

hato╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠ ╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠
╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠ ╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠
╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠╠ ╠╠╠☺

And the third problem is that when i shutdown the client the server prints out until i close it the phrase :

Our socket exists and here is what it wants to say:


Our socket exists and here is what it wants to say:


Our socket exists and here is what it wants to say:


Our socket exists and here is what it wants to say:


Our socket exists and here is what it wants to say:


Our socket exists and here is what it wants to say:

Can anyone help me fix some of these problems ?

Thanks in advance.

Run this, see what it produces.

Code:

#include<stdio.h>
int main ( ) {
  char buff[100];
  printf("%d %d\n", (int)sizeof(buff), (int)sizeof(&buff) );
  return 0;
}

Then study your (ab)use of sizeof.

Hmm you are right.. It prints out different numbers.. Ok problem No 2 fixed

Thanks a lot.

> recv(NewSocket,RcvBuff,200,0);
Next problem - if recv() actually fills the whole buffer, there is no \0 at the end for you to print with printf(%s)

Consider this.

Code:

n = recv(NewSocket,RcvBuff,sizeof(RcvBuff)-1,0);
if ( n > 0 ) {
  RcvBuff[n] = '\0';
}

No messy code to clear a buffer about to be overwritten anyway, and proper error checking as well.

Add the other return results from recv() to complete.

Sorry but i didn't understand exactly how this fix my problem.

I change to this my code:

Code:

if(FD_ISSET(NewSocket,&fdread))
					{
						printf("Our socket exists and here is what it wants to say:\n\n");

						// Recieving data from socket

						memset(&RcvBuff,0,sizeof(RcvBuff));
						RecvBytes = recv(NewSocket,RcvBuff,sizeof(RcvBuff)-1,0);

						if (RecvBytes > 0)
						{
							RcvBuff[RecvBytes] = '\0';
							printf("%s\n", RcvBuff);
						}

					}

and as i can understand we just put a \0 at the end of RcvBuff[] . Can't understand what changed. Still i can't connect two clients.

Maybe i didn't understood exactly what you said...:s

Thanks .

Like I said, you also need to check when recv() returns 0, as this indicates the remote has disconnected.

Not forgetting that -1 is also an error.

> RcvBuff[RecvBytes] = '\0';
When you have this, the memset is pointless.

here is the code now and its working good except from that i can't connect a second client .
What if i put the listen function in a loop to make it listening continuously?

Code:

if(FD_ISSET(NewSocket,&fdread))
					{
						// Recieving data from socket

						//memset(&RcvBuff,0,sizeof(RcvBuff));
						RecvBytes = recv(NewSocket,RcvBuff,sizeof(RcvBuff)-1,0);

						if (RecvBytes > 0)
						{
							printf("Our socket exists and here is what it wants to say:\n\n");
							RcvBuff[RecvBytes] = '\0';
							printf("%s\n", RcvBuff);
						}else if(RecvBytes == 0){
							printf("Client Disconnected");
							break;
						}else{
							printf("Error"); 
							break;
						}

					}

Thanks a lot for your help Salem..