client.c

// WIN SOCK - TCP Client example
#include <winsock2.h>
#include <stdio.h>

#if define UNICDOE
	#define wsprintf wsprintfW
#else
	#define wsprintf wsprintfA
#endif

SOCKET init_tcp()
{
	WSADATA wsaData;
	//Check if Operating System support WS2_32.LIB
	int retval = WSAStartup(0x202,   // version number 2.2
		&wsaData // struct contain DLL configuration information
		);
	if (retval != 0)
	return INVALID_SOCKET;
	printf("Server: WSAStartup() is OK.\n");
	//=======================================================
	// TCP socket
	SOCKET channel = socket(AF_INET, // AF_INET = TCP/IP   | PF_INET
		SOCK_STREAM,// SOCK_STREAM = TCP  | SOCK_DGRAM = UDP
		0 // 0 when use AF_INET
		);
	if (channel == INVALID_SOCKET)
		return INVALID_SOCKET;
	return channel;
}

SOCKET open_tcp(SOCKET channel, char *server_ip, unsigned short server_port)
{
	unsigned int addr = inet_addr(server_ip);
	struct hostent *hp;
	hp = gethostbyaddr((char *)&addr, 4, AF_INET);
	if (hp == NULL)
		return INVALID_SOCKET;
	printf("Client: gethostbyaddr() is OK.\n");
	// Copy the resolved information into the sockaddr_in structure
	struct sockaddr_in server;
	memset(&server, 0, sizeof(server));
	memcpy(&(server.sin_addr), hp->h_addr, hp->h_length);
	server.sin_family = hp->h_addrtype;
	server.sin_port = htons(server_port);

	printf("Client: Client connecting to: %s.\n", hp->h_name);
	if (connect(channel, (struct sockaddr*)&server, sizeof(server)) == SOCKET_ERROR)
		return INVALID_SOCKET;
	printf("Client: connect() is OK.\n");
	return channel;
}

int recieve_tcp(SOCKET channel, char Buffer[],int length)
{
	int retval = recv(channel, Buffer, length, 0);
	if (retval == SOCKET_ERROR)
		return SOCKET_ERROR;
	return retval;// number of bytes recieved
}

int send_tcp(SOCKET channel, char Buffer[],int length)
{
	int retval = send(channel, Buffer, length, 0);
	if (retval == SOCKET_ERROR)
		return SOCKET_ERROR;
	return retval;// number of bytes recieved
}

int main(int argc, char **argv)
{
	SOCKET channel = init_tcp();
	if (channel == INVALID_SOCKET)
	{
		printf("Client: init socket failed: error %d\n", WSAGetLastError());
		return -1;
	}
	//===============================
	char *server_ip = "127.0.0.1";
	unsigned short server_port = 5656;
	open_tcp(channel, server_ip, server_port);
	if (channel == INVALID_SOCKET)
	{
		printf("Client: open socket failed: error %d\n", WSAGetLastError());
		return -1;
	}
	//===============================
	// Test sending some string
	printf("Please enter your message:\n");
	char line[1024];  /* Generously large value for most situations */
	line[0] = '\0'; /* Ensure empty line if no input delivered */
	line[sizeof(line)-1] = ~'\0';  /* Ensure no false-null at end of buffer */
	fgets(line, sizeof(line), stdin);
	//===============================
	char Buffer[128];
	wsprintf(Buffer, line);

	int retval = send_tcp(channel, Buffer,sizeof(Buffer));
	if (retval == SOCKET_ERROR)
		printf("Client: send() failed: error %d\n", WSAGetLastError());
	
	memset(&Buffer, 0, sizeof(Buffer));
	retval = recieve_tcp(channel, Buffer, sizeof(Buffer));
	if (retval == SOCKET_ERROR)
	{
		printf("Client: recieved from socket failed: error %d\n", WSAGetLastError());
		closesocket(channel);
	}
	else if (retval == 0)
	{
		printf("Client: Server closed connection.\n");
		closesocket(channel);
		WSACleanup();
		return -1;
	}
	else
		printf("Client: Received: %d bytes, data from server: %s \n", retval, Buffer);
	system("pause");
	return 0;
}