Thread: Send/Recv

This is what I have:

Code:

/*
	Application:	Chat Client v1.0
	By:				Brian Denys
	Email:			[email protected]
*/

/*	Include Files	*/
#include <winsock2.h>
#include <stdio.h>
#pragma comment(lib, "ws2_32")

#define BACKLOG 5

int __cdecl Send_to_Client(const char *ip, unsigned short Port, char *Message)
{
	/*	Declare and Initialize variables	*/
	int iResult;
	WSADATA wsaData;
	SOCKET ConnectSocket;
	struct sockaddr_in clientConnect;

	/*	Initialize Winsock	*/
	iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
	if(iResult != NO_ERROR)
	{
		printf("WSAStartup() failed.\n");
		return 1;
	}

	/*	Create socket to connect to server	*/
	ConnectSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
	if(ConnectSocket == INVALID_SOCKET)
	{
		printf("Failed to create ConnectSocket.\n");
		WSACleanup();
		return 1;
	}

	/*	IP Address of client to send to	*/
	clientConnect.sin_family = AF_INET;
	clientConnect.sin_addr.s_addr = inet_addr( ip );
	clientConnect.sin_port = htons ( Port );

	/*	Connect to client	*/
	iResult = connect(ConnectSocket, (SOCKADDR*)&clientConnect, sizeof(clientConnect));
	if(iResult == SOCKET_ERROR)
	{
		printf("Failed to connect to client.\n");
		closesocket(ConnectSocket);
		WSACleanup();
		return 1;
	}

	/*	Send buffer	*/
	iResult = send(ConnectSocket, Message, (int)strlen(Message), 0);
	if(iResult == SOCKET_ERROR)
	{
		printf("Failed to send buffer.\n");
		closesocket(ConnectSocket);
		WSACleanup();
		return 1;
	}else{
		printf("Bytes send: &#37;d.", iResult);
	}
	
	/*	Shutdown the connection	*/
	iResult = shutdown(ConnectSocket, SD_SEND);
	if(iResult == SOCKET_ERROR)
	{
		printf("Shutdown connection failed.\n");
		closesocket(ConnectSocket);
		WSACleanup();
		return 1;
	}

	/*	Cleanup	*/
	closesocket(ConnectSocket);
	WSACleanup();

}

int __cdecl Receive_from_Client(const char *ip, unsigned short Port)
{
	/*	Declare and initialize variables	*/
	int iResult;
	WSADATA wsaData;
	SOCKET ConnectSocket;
	struct sockaddr_in clientRecv;
	int recvbuflen = 512;
	char recvbuf[512];

	/*	Initialize Winsock	*/
	iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
    if (iResult != NO_ERROR) {
      printf("WSAStartup() failed.\n");
      return 1;
    }

	/*	Create a socket to connect to client	*/
	ConnectSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (ConnectSocket == INVALID_SOCKET) {
        printf("socket() failed.\n");
        WSACleanup();
        return 1;
    }

	/*	IP Address and Port of the Client to connect to	*/
	clientRecv.sin_family = AF_INET;
    clientRecv.sin_addr.s_addr = inet_addr( ip );
    clientRecv.sin_port = htons( Port );

	/*	Connect to client	*/
	iResult = connect( ConnectSocket, (SOCKADDR*) &clientRecv, sizeof(clientRecv) );
    if ( iResult == SOCKET_ERROR) {
        closesocket (ConnectSocket);
        printf("Connect to client failed.\n");
        WSACleanup();
        return 1;
    }

	/*	Receive from Client	*/
	iResult = recv(ConnectSocket, recvbuf, recvbuflen, 0);
	printf("Received: %d\n", iResult);

	/*	Shutdown the connection	*/
	iResult = shutdown(ConnectSocket, SD_SEND);
	if(iResult == SOCKET_ERROR)
	{
		printf("Shutdown connection failed.\n");
		closesocket(ConnectSocket);
		WSACleanup();
		return 1;
	}

	/*	Cleanup	*/
	closesocket(ConnectSocket);
	WSACleanup();

}

int Listen_for_Client(unsigned short Port)
{
	/*	Declare and initialize variables	*/
	int iResult;
	WSADATA wsaData;
	SOCKET ConnectSocket;
	struct sockaddr_in clientListen;

	/*	Initialize Winsock	*/
	iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
    if (iResult != NO_ERROR) {
      printf("WSAStartup() failed.\n");
      return 1;
    }

	/*	Create a socket to connect to client	*/
	ConnectSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (ConnectSocket == INVALID_SOCKET) {
        printf("socket() failed.\n");
        WSACleanup();
        return 1;
    }

	/*	IP Address and Port of the Client to connect to	*/
	clientListen.sin_family = AF_INET;
    clientListen.sin_addr.s_addr = htonl(INADDR_ANY);
    clientListen.sin_port = htons( Port );

	/*	Bind	*/
	iResult = bind(ConnectSocket, (SOCKADDR*)&clientListen, sizeof(clientListen));
	if(iResult == SOCKET_ERROR)
	{
		printf("bind() failed.\n");
		closesocket(ConnectSocket);
		WSACleanup();
		return 1;
	}

	/*	Listen	*/
	iResult = listen(ConnectSocket, BACKLOG);
	if(iResult == SOCKET_ERROR)
	{
		printf("listen() failed.\n");
		closesocket(ConnectSocket);
		WSACleanup();
		return 1;
	}

	printf("Listening on socket ..\n");

	/*	Cleanup	*/
	WSACleanup();

}

void Create1()
{
		Send_to_Client("127.0.0.1", 1111, "Test.");
}

void Create2()
{
	Receive_from_Client("127.0.0.1", 1111);
}

void Create3()
{
	Listen_for_Client(1111);
}

int __cdecl main()
{
	CreateThread(NULL, 0, (unsigned long(__stdcall*)(void*))Create3, NULL, 0, NULL);
	CreateThread(NULL, 0, (unsigned long(__stdcall*)(void*))Create2, NULL, 0, NULL);
	CreateThread(NULL, 0, (unsigned long(__stdcall*)(void*))Create1, NULL, 0, NULL);

	system("pause");
	return 0;
}

I don't receive the msg i just send, why?

you do not send the null termination.
So obviously - you do not receive it

Or - while printing add preceision to your format to print exactly the same number of chars you have received

Or add the null terminator manually - after the last received character before printing (check for memory overrun in this solution)

Thanks got that working =]
Now i still have to make a chat client from that =]

If you want to process several connections - maybe better to start work asynchrony on the select

Do you mean aside from you not allocating any memory for Msg?

--
Mats

Originally Posted by brietje698

Unhandled exception at 0x104e63b1 in Chat.exe: 0xC0000005: Access violation writing location 0xcccccccc.

Yes, let me guess that "Msg" happens to be 0xcccccccc when you do this? Have you tried actually single-stepping into the function, rather than asking here? Do you understand how cin and printf() uses memory?

You have not set Msg to a valid memory location to write to, and since Visual Studio ensures that uninitialized variables are still set to a defined value, you get this, rather than just randomly overwriting something in your memory - much better, I think.

--
Mats

That's because Msg points to one byte (assuming char is 1 byte) of memory. You are assuming it is pointing to a chunk of memory big enough to hold whatever is inputted. The program may or may not crash depending on who or what owns the memory directly after the 1 byte pointed to by Msg. If you want to make sure that you have a chunk of memory you need to ALLOCATE it.

in C:

Code:

Msg = malloc(sizeof(char) * HoweverManyCharactersYouExpect);

in C++

Code:

Msg = new char[HoweverManyCharacterYouExpect];