Question

我创建了单个服务器和单个客户端回显应用程序。它适用于单个服务器和单个客户端。但是现在我想通过为单个服务器处理多个客户端来使其更加实用。我遇到了在服务器端使用listen（）函数来处理多个客户端连接的想法，但后来我才知道listen只用于TCP。请帮助我。下面是我的单个服务器和单个客户端的功能代码。帮助我如何修改它以生成单服务器多客户端应用程序。

服务器：

#define PORT 8888   //The port on which to listen for incoming data

int main()
{

SOCKET s;
struct sockaddr_in serverSocket, clientSocket;

char receiveBuffer[1000];
//int receiveBufferLength=1000;
int clientSocketLength;
int recv_len;

clientSocketLength = sizeof(clientSocket) ;

WSADATA wsa; 
//Initialise winsock
printf("\nInitialising Winsock...");
if (WSAStartup(MAKEWORD(2,2),&wsa) != 0)
{
  printf("Failed. Error Code : %d",WSAGetLastError());
    exit(EXIT_FAILURE);
}
printf("Socket Initialised.\n");

//Create a socket
if((s = socket(AF_INET , SOCK_DGRAM , 0 )) == INVALID_SOCKET)
{
    printf("Could not create socket : %d" , WSAGetLastError());
}
printf("Socket created.\n");   

//Prepare the sockaddr_in structure
serverSocket.sin_family = AF_INET;
serverSocket.sin_addr.s_addr = INADDR_ANY;
serverSocket.sin_port = htons( PORT );

//Bind
if( bind(s ,(struct sockaddr *)&serverSocket , sizeof(serverSocket)) == SOCKET_ERROR)
{
    printf("\nBind failed with error code : %d" , WSAGetLastError());
    exit(EXIT_FAILURE);
}
printf("Bind done\n\n");

//keep listening for data

while(1)
{
    printf("\n\t\t\tWaiting for data...\n");
    fflush(stdout);
    //receiveBuffer[2000]=NULL;

    if((recv_len = recvfrom(s, receiveBuffer, 1000, 0, (struct sockaddr *) &clientSocket, &clientSocketLength)) == SOCKET_ERROR)
    {
        printf("\n\nrecvfrom() failed with error code : %d" , WSAGetLastError());
        //exit(EXIT_FAILURE);
        while(1);
    }

    //print details of the client/peer and the data received
    printf("\n\nReceived packet from %s:%d\n", inet_ntoa(clientSocket.sin_addr), ntohs(clientSocket.sin_port));
    printf("\nClient Says: " );
        printf(receiveBuffer,recv_len);



    //now reply the client with the same data
    if (sendto(s, receiveBuffer, recv_len, 0, (struct sockaddr*) &clientSocket, clientSocketLength) == SOCKET_ERROR)
    {
        printf("\nsendto() failed with error code : %d" , WSAGetLastError());
       // exit(EXIT_FAILURE);
        while(1);
    }
    else
        printf("\nMessage Sent Back to Client");

}

closesocket(s);
WSACleanup();
return 0;

}

客户端：

#define PORT 8888   //The port on which to listen for incoming data
#define SERVER "10.0.1.25"  //ip address of udp server
//#define PORT 8888   //The port on which to listen for incoming data

int main(void)
{
struct sockaddr_in connectedSocket;

int s;
int length=sizeof(connectedSocket);

char receiveBuffer[1000];
char message[1000];

//clear the buffer by filling null, it might have previously received data
memset(receiveBuffer,'\0', 1000);

WSADATA wsa;
//Initialise winsock
printf("\nInitialising Winsock...\n");
if (WSAStartup(MAKEWORD(2,2),&wsa) != 0)
{
    printf("\nFailed. Error Code : %d",WSAGetLastError());
    exit(EXIT_FAILURE);
}
printf("\n.........Initialised.\n");


//create socket
if ( (s=socket(AF_INET, SOCK_DGRAM, 0)) == SOCKET_ERROR)
{
    printf("\n\nsocket() failed with error code : %d" , WSAGetLastError());
    exit(EXIT_FAILURE);
}


//setup address structure
memset((char *) &connectedSocket, 0, sizeof(connectedSocket));
connectedSocket.sin_family = AF_INET;
connectedSocket.sin_port = htons(PORT);
 //connectedSocket.sin_port = INADDR_BROADCAST;
connectedSocket.sin_addr.S_un.S_addr = inet_addr(SERVER);

while(1)
{
    printf("\n\n\nEnter message : ");
    gets(message);

  //send the message
    if (sendto(s, message,sizeof(message) , 0 , (struct sockaddr *) &connectedSocket, sizeof(connectedSocket)) == SOCKET_ERROR)
    {
        printf("\nsendto() failed with error code : %d" , WSAGetLastError());
        exit(EXIT_FAILURE);
    }

        printf("\nMessage Successfully sent to Server");
      // fflush(stdout);

    if (recvfrom(s, receiveBuffer, 1000, 0, (struct sockaddr *) &connectedSocket,&length) == SOCKET_ERROR)
    {
       printf("\nrecvfrom() failed with error code : %d" , WSAGetLastError());
       exit(EXIT_FAILURE);
    }

    printf("\nServer Says : ");
    printf(receiveBuffer,sizeof(receiveBuffer));

}

closesocket(s);
WSACleanup();

return 0;

}

Answer 1

让我向你解释一些可能令人困惑的事情。

首先，在您的服务器中，即使您要广播，也需要将serverSocket.sin_addr.s_addr设置为INADDR_ANY。你不想让它INADDR_BROADCAST。这只是告诉服务器绑定计算机上的任何 IP地址，导致一台计算机可以拥有多于1个IP。你正确地做了什么。

但是如何从服务器广播？您需要将setsockopt与SO_BROADCAST参数一起使用，如此...

int options = 1;
if ((setsockopt(s, SOL_SOCKET, SO_BROADCAST,(char *)&options,sizeof(options))) < 0){
    printf("%d",WSAGetLastError());
}

这将使您的服务器侦听进行广播，但您如何发送广播？在调用INADDR_BROADCAST函数之前，您需要在 sockaddr 结构的s_addr字段中设置sendto。

clientSocket.sin_addr.s_addr = INADDR_BROADCAST;

然后使用sendto与clientSocket一起制作麻烦。

其次，在您的客户端代码中，根据您的应用程序，您有两个选项。

如果您希望您的客户端首先向服务器发送消息（直接无需广播），那么您通过设置inet_addr(SERVER)正确地执行此操作，以便客户端仅将消息发送到您的服务器。 p>
但是，如果您希望客户端广播该消息，则需要在客户端中再次使用setsockopt，与服务器中相同，并在connectSocket结构中设置地址到INADDR_BROADCAST。

最后，如果你告诉我们你想在这里完成什么会更好。如果您希望客户端首先连接到服务器，那么服务器将客户端告知其他客户端，那么您可能需要使用TCP而不是UDP。

单个服务器，多个客户端在C中的UDP应用程序（Winsock）

1 个答案: