C++ socket编程：SENDTO（）和recvfrom（）错误代码10038＆在 '服务器' 绑定失败与10038

Question

//UDP receiver 
int main() 
{ 
    WSAData wsaData; 
    SOCKET receivingSocket; 
    SOCKADDR_IN receiverAddr; 
    SOCKADDR_IN senderAddr; 
    int senderAddrSize = sizeof(senderAddr); 
    int port=51020; 
    char receiveBuf[1024]; 
    int bufLength=1024; 

    cout << "UDP receiver\n"; 

    //Initialize winsock 
    if (WSAStartup(MAKEWORD(2,2),&wsaData) != 0) 
    { 
     cout << "Failed. Error Code : " << WSAGetLastError(); 
     exit(EXIT_FAILURE); 
    } 
    cout << "Initialised\n";` 

    if(receivingSocket = socket(AF_INET, SOCK_DGRAM, 0) == INVALID_SOCKET) 
    { 
     cout << "Could not create socket :" << WSAGetLastError(); 
    } 
    cout << "Socket created.\n"; 

    //fill up SOCKADDR_IN structure 
    senderAddr.sin_port = htons(port); 
    senderAddr.sin_family = AF_INET; 
    senderAddr.sin_addr.s_addr = htonl(INADDR_ANY); 

    //Bind information with socket 
    bind(receivingSocket, (SOCKADDR*)&senderAddr, sizeof(senderAddr)); 

    while(1) 
    { 
     cout << "Waiting for message\n"; 

     //try to receive some data, this is a blocking call 
     if (recvfrom(receivingSocket, receiveBuf, 1024, 0, (SOCKADDR*)&senderAddr, &senderAddrSize)) == SOCKET_ERROR)) 
     { 
      cout << "recvfrom() failed with error code :" << WSAGetLastError(); 
      exit(EXIT_FAILURE); 
     } 
     cout << receiveBuf; 
    } 

    //Close socket 
    closesocket(receivingSocket); 
    WSACleanup(); 
    std::cin.get(); 
    return 0; 
} 

//UDP server 
int main() 
{ 
    WSAData wsaData; 
    SOCKET sendingSocket; 
    SOCKADDR_IN receiverAddr; 
    int port = 51010; 
    char sendBuf[1024]="Hello!!!"; 
    int bufLength = 1024; 

    cout << "UDP server from book\n"; 

    //Initialize socket 
    if (WSAStartup(MAKEWORD(2,2),&wsaData) != 0) 
    { 
     cout << "Failed. Error Code : " << WSAGetLastError(); 
     exit(EXIT_FAILURE); 
    } 
    cout << "Initialised\n"; 

    if(sendingSocket = socket(AF_INET, SOCK_DGRAM, 0) == INVALID_SOCKET) 
    { 
     cout << "Could not create socket : " << WSAGetLastError(); 
    } 
    cout << "Socket created.\n"; 

    //FIll out structure of receiverAdd 
    receiverAddr.sin_family = AF_INET; 
    receiverAddr.sin_port = htons(port); 
    receiverAddr.sin_addr.s_addr = inet_addr("192.168.1.100"); 

    int test = bind(sendingSocket, (SOCKADDR*)&receiverAddr, sizeof(receiverAddr)); 
    if(test < 0) 
    { 
     cout << "Bind failed with error code : %d" << WSAGetLastError(); 
     exit(EXIT_FAILURE); 
    } 
    cout << "Bind is successful\n"; 

    while(1) 
    { 
     cout << "Sending data...\n"; 

     //Send datagram to receiver 
     if(sendto(sendingSocket, sendBuf, 1024, 0, (SOCKADDR*)&receiverAddr, sizeof(receiverAddr)) == SOCKET_ERROR) 
     { 
      cout << "sendto() failed with error code : " << WSAGetLastError(); 
      exit(EXIT_FAILURE); 
     } 
     cout << "Sent"; 
    } 

    //close socket 
    closesocket(sendingSocket); 

    WSACleanup(); 

    std::cin.get(); 

    // return 0; 
} 

Answer 1

错误10038是WSAENOTSOCK: The descriptor is not a socket.

要调用socket()和分配您的SOCKET处理if语句的内部，但是您缺少足够的括号。他们应该是这样的，而不是：

if((receivingSocket = socket(AF_INET, SOCK_DGRAM, 0)) == INVALID_SOCKET) 

if((sendingSocket = socket(AF_INET, SOCK_DGRAM, 0)) == INVALID_SOCKET) 

就个人而言，我讨厌执行的if语句像这里面的分配代码。我宁愿将它们分开。它是清洁，容易出错少，没有效率较低，从编译器的角度来看：

receivingSocket = socket(AF_INET, SOCK_DGRAM, 0); 
if(receivingSocket == INVALID_SOCKET) 

sendingSocket = socket(AF_INET, SOCK_DGRAM, 0); 
if(sendingSocket == INVALID_SOCKET) 

在一个侧面说明：

1. WSAStartup()不适合使用WSAGetLastError()错误报告，它直接返回错误代码。这在WSAStartup()文档中有明确说明。进入recvfrom()循环之前

   int err = WSAStartup(MAKEWORD(2,2),&wsaData); 
   if (err != 0) 
   { 
       cout << "Failed. Error Code : " << err; 
       exit(EXIT_FAILURE); 
   } 
   

2. 您的UDP接收器不检查的bind()一个错误的返回值。