Question

我的情况如下：我有一台运行UDP多播服务器的Windows机器正在广播数据包。我编写了一个窗口客户端，能够在连接到网络的单独Windows机器上捕获这些数据包而不会出现问题。我在Windows机器上遇到了一些防火墙问题，但是解决了这个问题。

现在，我有一个ubuntu 12.04版本的客户端;但是，我的程序没有找到这些数据包。我浏览了其他堆栈溢出帖子和一些谷歌线程提供的所有建议：

当我运行客户端时，netstat -g显示多播网络的IP地址
我使用sysctl
使用tcpdump -i wlan0
添加了一条路线（sudo route add -net 224.0.0.0 netmask 224.0.0.0 wlan0）

对于第四步，这是通过wlan0建立的无线连接，所以我在wlan0上添加路由。同样，wlan0＆＃39; rp_filter = 0。

现在，代码。从打印语句和错误检查。我看到我成功绑定，加入多播组，创建缓冲区等...然后它只是阻塞recvfrom（）函数调用。

#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <cstring>
#include <unistd.h>
#include <pthread.h>
#include <fstream>

#pragma warning( disable : 4996 )

#define MAX_PACKETSIZE              100000  // max size of packet (actual packet size is dynamic)

bool IPAddress_StringToAddr(char *szNameOrAddress, struct in_addr *Address);
void Unpack(char* pData);

#define MULTICAST_ADDRESS       "239.255.42.99"     // IANA, local network
#define PORT_COMMAND            1510
#define PORT_DATA               1511                
#define SOCKET_ERROR -1
#define INVALID_SOCKET -1

typedef int SOCKET;
SOCKET DataSocket;

int main(int argc, char* argv[])
{
    int retval;
    char szMyIPAddress[128] = "";
    in_addr MyAddress, MultiCastAddress;
    int optval = 0x100000;
    int optval_size = 4;


    // client address
    if(argc>1)
    {
        strcpy(szMyIPAddress, argv[1]); // specified on command line
        IPAddress_StringToAddr(szMyIPAddress, &MyAddress);
    }
    else
    { printf("usage: ./client [local_ip_address]\n"); return 0; }

    MultiCastAddress.s_addr = inet_addr(MULTICAST_ADDRESS);   
    printf("Client: %s\n", szMyIPAddress);
    printf("Multicast Group: %s\n", MULTICAST_ADDRESS);

    // create a "Data" socket
    printf("Create Socket.\n");
    DataSocket = socket(AF_INET, SOCK_DGRAM, 0);

    // allow multiple clients on same machine to use address/port
    int value = 1;
    printf("Set SO_REUSEADDR sockopt.\n");
    retval = setsockopt(DataSocket, SOL_SOCKET, SO_REUSEADDR, (char*)&value, sizeof(value));
    if (retval == SOCKET_ERROR)
    {
        close(DataSocket);
        return -1;
    }

    //bind
    struct sockaddr_in MySocketAddr;
    memset(&MySocketAddr, 0, sizeof(MySocketAddr));
    MySocketAddr.sin_family = AF_INET;
    MySocketAddr.sin_port = htons(PORT_DATA);
    MySocketAddr.sin_addr = MyAddress;
    printf("Bind Socket.\n");
    if (bind(DataSocket, (struct sockaddr *)&MySocketAddr, sizeof(struct sockaddr)) == SOCKET_ERROR)
    {
        printf("[PacketClient] bind failed.\n");
        return 0;
    }

    // join multicast group
    struct ip_mreq Mreq;
    Mreq.imr_multiaddr = MultiCastAddress;
    Mreq.imr_interface = MyAddress;
    printf("Join multicast group.\n");
    retval = setsockopt(DataSocket, IPPROTO_IP, IP_ADD_MEMBERSHIP, (char *)&Mreq, sizeof(Mreq));
    if (retval == SOCKET_ERROR)
    {
        printf("[PacketClient] join failed.\n");
        return -1;
    }

    // create a 1MB buffer
    printf("Create 1MB Buffer.\n");
    setsockopt(DataSocket, SOL_SOCKET, SO_RCVBUF, (char *)&optval, 4);
    getsockopt(DataSocket, SOL_SOCKET, SO_RCVBUF, (char *)&optval, (socklen_t*)&optval_size);
    if (optval != 0x100000)
    {
        printf("[PacketClient] ReceiveBuffer size = %d\n", optval);
    } 

    //listening
    printf("Listening...\n");
    char  szData[20000];
    int addr_len = sizeof(struct sockaddr);
    sockaddr_in TheirAddress;
    while (1)
    {
        // Block until we receive a datagram from the network (from anyone including ourselves)
        int nDataBytesReceived = recvfrom(DataSocket, szData, sizeof(szData), 0, (sockaddr *)&TheirAddress, (socklen_t*)&addr_len);

        Unpack(szData);
    }

    return 0;
}

// convert ipp address string to addr
bool IPAddress_StringToAddr(char *szNameOrAddress, struct in_addr *Address)
{
    int retVal;
    struct sockaddr_in saGNI;
    char hostName[256];
    char servInfo[256];
    u_short port;
    port = 0;

    // Set up sockaddr_in structure which is passed to the getnameinfo function
    saGNI.sin_family = AF_INET;
    saGNI.sin_addr.s_addr = inet_addr(szNameOrAddress);
    saGNI.sin_port = htons(port);

    // getnameinfo
    if ((retVal = getnameinfo((sockaddr *)&saGNI, sizeof(sockaddr), hostName, 256, servInfo, 256, NI_NUMERICSERV)) != 0)
    {
        printf("[PacketClient] GetHostByAddr failed.\n");
        return false;
    }

    Address->s_addr = saGNI.sin_addr.s_addr;

    return true;
}

void Unpack(char* pData)
{
    printf("Begin Packet\n-------\n");
}

任何建议都表示赞赏。以下是我在尝试解决此问题时用作参考的问题：UDP socket (multicast) not receiving data (Ubuntu)

Answer 1

我在这里粘贴我的答案，而不是在评论中写下来。

据我所知，你们两边都有Windows机器，成功播放udp数据包，现在你想用ubuntu机器替换它们。并且机器正在接收数据包，但不会通知您的客户端。

也许这会有所帮助

SOL_SOCKET用于套接字层，IPPROTO_IP用于IP层等...对于多播编程，级别始终为IPPROTO_IP

以下是简化的RIPv2协议的工作代码，可以毫无问题地发送和重新发送多播流量。

int setup_sender_connection(struct in_addr interface_addr){
    //create socket
    int sock = socket(AF_INET, SOCK_DGRAM, 0);
    if(sock<0){
        die("Creating Socket");
    }

    //set outgoing interface
    if(setsockopt(sock, IPPROTO_IP, IP_MULTICAST_IF, &interface_addr, sizeof(interface_addr))<0){
        die("Setting outgoing interface");
    }

    //disable loopback
    u_char loop = 0;
    if(setsockopt(sock, IPPROTO_IP, IP_MULTICAST_LOOP, &loop, sizeof(loop))<0){
        die("Disabling loopback");
    }

    //allow reusing of port
    int reuse = 1;
    if(setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (char *)&reuse, sizeof(reuse)) < 0){  
        die("Allowing reuse");
    }

    //bind to this port
    struct sockaddr_in saddr;
    bzero(&saddr, sizeof(struct sockaddr_in));

    saddr.sin_family = AF_INET;
    saddr.sin_port = htons(520); 
    saddr.sin_addr = interface_addr;

    if(bind(sock, (struct sockaddr *)&saddr, sizeof(struct sockaddr_in))<0){
        die("Binding");
    }
    return sock;
}

void join_group(int sock, struct in_addr interface_addr){
    //join gorup
    struct ip_mreq mreq;
    bzero(&mreq, sizeof(struct ip_mreq));

    mreq.imr_multiaddr.s_addr = inet_addr(MULTICAST_IP);    /* IP multicast address of group */
    mreq.imr_interface = interface_addr;            /* local IP address of interface */

    if(setsockopt(sock, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq))<0){
        die("Joining group");
    }
}

void die(char *error){
    perror(error);
    exit(1);
}

在Ubuntu上进行多播

1 个答案: