Question

我在这里有两个代码用于与广播机制进行UDP聊天，其中服务器可以同时向所有客户端广播消息

服务器代码......

    #include<stdio.h>
#include<string.h>
#include<sys/stat.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
int main(int argc, char *argv[] )
{
    struct sockaddr_in client,server;
    int s,n;
    char b1[100],b2[100];
    s=socket(AF_INET,SOCK_DGRAM,0);
    server.sin_family=AF_INET;
    server.sin_port=htons(2000);
    server.sin_addr.s_addr=inet_addr("127.0.0.1");
    bind(s,(struct sockaddr *)&server,sizeof(server));
    printf("\nServer ready,waiting for client....\n");
    n=sizeof(client);
    int sock;                         /* Socket */
    struct sockaddr_in broadcastAddr; /* Broadcast address */
    char *broadcastIP;                /* IP broadcast address */
    unsigned short broadcastPort;     /* Server port */
    char *sendString;                 /* String to broadcast */
    int broadcastPermission;          /* Socket opt to set permission to broadcast */
    unsigned int sendStringLen;       /* Length of string to broadcast */

    if (argc < 4)                     /* Test for correct number of parameters */
    {
        fprintf(stderr,"Usage:  %s <IP Address> <Port> <Send String>\n", argv[0]);
        exit(1);
    }

    broadcastIP = argv[1];            /* First arg:  broadcast IP address */ 
    broadcastPort = atoi(argv[2]);    /* Second arg:  broadcast port */
    sendString = argv[3];             /* Third arg:  string to broadcast */

    /* Create socket for sending/receiving datagrams */
    sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
     broadcastPermission = 1;
    while(1)
    {
        recvfrom(s,b1,sizeof(b1),0,(struct sockaddr *) &client,&n);
        if(!(strcmp(b1,"end")))
            break;
        printf("\nClient:%s",b1);
        printf("\nServer:");
        gets(b2);
        sendto(s,b2,sizeof(b2),0,(struct sockaddr *) &client,n);
     broadcastPermission = 1;
    setsockopt(sock, SOL_SOCKET, SO_BROADCAST, (void *) &broadcastPermission,sizeof(broadcastPermission));
           /* Construct local address structure */
    //memset(&broadcastAddr, 0, sizeof(broadcastAddr));   /* Zero out structure */
    broadcastAddr.sin_family = AF_INET;                 /* Internet address family */
    broadcastAddr.sin_addr.s_addr = inet_addr(broadcastIP);/* Broadcast IP address */
    broadcastAddr.sin_port = htons(broadcastPort);         /* Broadcast port */
    sendStringLen = strlen(sendString);
    for (;;) /* Run forever */
        {
         /* Broadcast sendString in datagram to clients every 3 seconds*/
         sendto(sock, sendString, sendStringLen, 0, (struct sockaddr *) &broadcastAddr, sizeof(broadcastAddr));
         //    DieWithError("sendto() sent a different number of bytes than expected");

        //sleep(3);   /* Avoids flooding the network */
     }




    }

}

客户端代码......

#include<stdio.h>
#include<string.h>
#include<sys/stat.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>

#define MAXRECVSTRING 255
int main(int argc , char argv[])
{
    struct sockaddr_in client,server;
    int s,n;
    char b1[100],b2[100];
    s=socket(AF_INET,SOCK_DGRAM,0);
    server.sin_family=AF_INET;
    server.sin_port=htons(2000);
    server.sin_addr.s_addr=inet_addr("127.0.0.1");
    printf("\nClient ready....\n");
    n=sizeof(server);
    int sock;                         /* Socket */
    struct sockaddr_in broadcastAddr; /* Broadcast Address */
    unsigned short broadcastPort;     /* Port */
    char recvString[MAXRECVSTRING+1]; /* Buffer for received string */
    int recvStringLen;                /* Length of received string */

    if (argc != 2)    /* Test for correct number of arguments */
    {
        fprintf(stderr,"Usage: %s <Broadcast Port>\n", argv[0]);
        exit(1);
    }
     printf("\nClient ready…11111.\n");
    broadcastPort = htons(argv[1]);   /* First arg: broadcast port */
     printf("\nClient ready….1\n");
    /* Create a best-effort datagram socket using UDP */
    if(sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)<0)
    printf("no sock created");  
     printf("\nClient ready….2\n");
    while(1)
    {
        printf("\nClient:");
        gets(b2);
        sendto(s,b2,sizeof(b2),0,(struct sockaddr *) &server,n);
        if(strcmp(b2,"end")==0)
            break;
        recvfrom(s,b1,sizeof(b1),0,NULL,NULL);
        printf("\nServer:%s",b1);
    broadcastAddr.sin_family = AF_INET;                 /* Internet address family */
    broadcastAddr.sin_addr.s_addr = htonl(INADDR_ANY);  /* Any incoming interface */
    broadcastAddr.sin_port = htons(broadcastPort);      /* Broadcast port */

    /* Bind to the broadcast port */
    bind(sock, (struct sockaddr *) &broadcastAddr, sizeof(broadcastAddr));


    /* Receive a single datagram from the server */
    recvStringLen = recvfrom(sock, recvString, MAXRECVSTRING, 0, NULL, 0);

    recvString[recvStringLen] = '\0';
    printf("Received: %s\n", recvString);    /* Print the received string */


    }
    close(sock);
}

这些代码运行没有任何错误但是当我从客户端向服务器发送字符串时，服务器无法接收字符串，反之亦然。

如果有人可以帮助我解决为什么会发生这种情况。

我在不同终端窗口的同一系统上运行服务器和客户端..因此本地主机地址

Answer 1

某些平台，例如Windows不会接收广播，除非套接字绑定到INADDR_ANY，即0.0.0.0。

Answer 2

首先：

server.sin_port=2000;

您忘了制作此网络订单。

Answer 3

在您的服务器代码中：套接字未绑定到任何IP地址。尽管它广播消息并且客户端接收；反之亦然。因此，将服务器和客户端套接字绑定到2个不同的IP地址。服务器广播消息时，请在sendto函数中使用适当的广播地址（请参阅服务器-客户端IP的子网）。

使用UDP协议从服务器向多个客户端广播消息

3 个答案: