TCP协议，两个socket绑定同个端口，需要使用setsockopt，以为UDP的不用，测试了下，如果第二个socket在bind之前不使用setsockopt，bind函数会返回-1。

如下面的代码

WORD sockVision = MAKEWORD(2, 2);
	WSADATA wsadata;
	SOCKET sclient;
	struct sockaddr_in clientAddr;
	char senddata[255];
	char revdata[255];
	int ret = -1;
	int len = -1;
	if (WSAStartup(sockVision, &wsadata) != 0)
	{
		printf("WSA初始化失败\n");
		system("pause");
		return 0;
	}

	sclient = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
	if (sclient == INVALID_SOCKET)
	{
		printf("socket客户端创建失败\n");
		system("pause");
		return 0;
	}
	
	int port = 7081;
	char str[16] = "47.112.212.215";
	
	clientAddr.sin_family = AF_INET;
	clientAddr.sin_port = htons(port);
	clientAddr.sin_addr.S_un.S_addr = inet_addr(str);
	len = sizeof(clientAddr);

	
	SOCKADDR_IN addrClient;
	addrClient.sin_family = AF_INET;
	addrClient.sin_addr.S_un.S_addr = inet_addr("0.0.0.0"); // 客户端地址 0.0.0.0
	addrClient.sin_port = htons(7777); // 客户端为7777端口

	BOOL bReuseaddr1 = TRUE;

	setsockopt(sclient, SOL_SOCKET, SO_REUSEADDR, (const char*)&bReuseaddr1, sizeof(BOOL));

	int clientbind = bind(sclient, (SOCKADDR*)&addrClient, sizeof(SOCKADDR)); 
	printf("clientbind  =  %d\n", clientbind);

															

	SOCKET serSocket;
	struct sockaddr_in remoteAddr;
	struct sockaddr_in sin;
	int nAddrlen = sizeof(remoteAddr);

	//绑定IP和端口
	sin.sin_family = AF_INET;
	sin.sin_port = htons(7777);
	sin.sin_addr.S_un.S_addr = INADDR_ANY;// inet_addr("127.0.0.1")

										 
	serSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
	if (serSocket == INVALID_SOCKET)
	{
		printf("socket服务器创建失败\n");
	}

	bReuseaddr1 = TRUE;

	setsockopt(serSocket, SOL_SOCKET, SO_REUSEADDR, (const char*)&bReuseaddr1, sizeof(BOOL));

	int serverbind = bind(serSocket, (LPSOCKADDR)&sin, sizeof(sin));
       printf("serverbind =  %d\n", serverbind);
	

输出

clientbind  =  0

serverbind  =  0

如果注释掉第二个setsockopt

输出

clientbind  =  0

serverbind  =  -1