getsockname : 獲取本機socket資訊 ( 源ip/port)

void get_out_int(char * ipaddr,unsigned short port)
{
    //windows 初始化一下;
    //WSADATA wsadata;
	// WSAStartup(MAKEWORD(2, 2), &wsadata);

	SOCKET sock = socket(AF_INET, SOCK_DGRAM, 0); // SOCK_STREAM 一樣
	SOCKADDR_IN sock_addr,local_addr;
	memset(&local_addr, 0, sizeof(local_addr));
	memset(&sock_addr, 0, sizeof(sock_addr));
	sock_addr.sin_addr.s_addr = inet_addr(ipaddr); 
	sock_addr.sin_port = htons(port);
	sock_addr.sin_family = AF_INET;
	if (connect(sock, (SOCKADDR*)&sock_addr, sizeof(sock_addr)) == SOCKET_ERROR) 
	{
		print_error(WSAGetLastError());
		closesocket(sock);
		return;
	}
	int len = sizeof(local_addr);
	getsockname(sock, (SOCKADDR*)&local_addr, &len); //獲取套接字源資訊
	closesocket(sock);
	printf("local addr:%s\n", inet_ntoa(local_addr.sin_addr));
}