为什么客户端没有收到此UDP单播？

Question

为什么客户没有收到此单播？我已经在这里捶打了好几个小时。 Grr ..;（

• 我以nn.dd的形式发送价格代码;例如，42.23,93.75。仅用于测试目的的5个字节。
• 服务器的（tick生成器）IP地址为192.168.1.101
• 客户的地址是192.168.1.102
• sendto命令的返回值为5，应该是。
• 我可以在两个方向成功ping：来自服务器的客户端和来自客户端的服务器;约3毫秒的响应时间。
• 两台机器都在同一个网络上。
• 正在生成并发送价格，如下所示
• 在同一台计算机上的客户端进程（具有相同的IP地址192.168.1.101）位于不同的终端，工作正常，如下面的代码段2所示。
• 完整代码包含在代码段3和4中
• Linksys WRT54GL v1.1 with stock BIOS
• 此代码是Beej的UDP示例的修改版本： http://beej.us/guide/bgnet/output/html/multipage/clientserver.html#datagram
• 注意：使用tickGenerator 192.168.1.101 helloWorld启动服务器（当然使用您的IP地址）。 ＆＃34; helloWorld＆＃34;来自Beej的例子将被忽略;我已经在随机价格生成器中入侵了。

勾选生成器输出：从192.168.1.101正确生成刻度数据：

Price unicasted: 49.58
Price unicasted: 50.00
Price unicasted: 50.24
...

客户端位于同一台计算机的单独终端窗口（也来自192.168.1.101）正确接收多播：

listener: waiting to recvfrom...
listener: got packet from 192.168.1.101
listener: packet is 5 bytes long
listener: packet contains "49.58"
listener: got packet from 192.168.1.101
listener: packet is 5 bytes long
listener: packet contains "50.00"
listener: got packet from 192.168.1.101
listener: packet is 5 bytes long
listener: packet contains "50.24"
...

192.168.1.102处的独立机器只是挂起......

勾选生成器：

/*
 ** talker.c -- a datagram "client" demo
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>

#include <time.h>
#include <stdlib.h>
#include <math.h>
#include <chrono>
#include <thread>
#include <iostream>

#define SERVERPORT "4950"    // the port users will be connecting to

void reverse(char *str, int len) {
    int i=0, j=len-1, temp;
    while (i<j)
    {
        temp = str[i];
        str[i] = str[j];
        str[j] = temp;
        i++; j--;
    }
}
int intToStr(int x, char str[], int d)
{
    int i = 0;
    while (x) {
        str[i++] = (x%10) + '0';
        x = x/10;
    }
    while (i < d)
        str[i++] = '0';

    reverse(str, i);
    str[i] = '\0';
    return i;
}
void ftoa(float n, char *res, int afterpoint) {
    int ipart = (int)n;
    float fpart = n - (float)ipart;
    int i = intToStr(ipart, res, 0);
    if (afterpoint != 0) {
        res[i] = '.';
        fpart = fpart * 100;
        intToStr((int)fpart, res + i + 1, afterpoint);
    }
}
float randPrice() {
    int b;
    float d;
    b = 4950 + rand() % 100 + 1;
    d = (float)b/100;
    return d;
}
int main(int argc, char *argv[])
{
    int sockfd;
    struct addrinfo hints, *servinfo, *p;
    int rv;
    int numbytes;

    if (argc != 3) {
        fprintf(stderr,"usage: talker hostname message\n");
        exit(1);
    }

    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_DGRAM;

    if ((rv = getaddrinfo(argv[1], SERVERPORT, &hints, &servinfo)) != 0) {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
        return 1;
    }

    // loop through all the results and make a socket
    for(p = servinfo; p != NULL; p = p->ai_next) {
        if ((sockfd = socket(p->ai_family, p->ai_socktype,
                             p->ai_protocol)) == -1) {
            perror("talker: socket");
            continue;
        }

        break;
    }

    if (p == NULL) {
        fprintf(stderr, "talker: failed to create socket\n");
        return 2;
    }

    char myPrice[6];
    float f;

    while(1) {
        f = randPrice();
        ftoa(f, myPrice, 2); // Convert price to string
        std::cout << "Price multicasted: " << myPrice << std::endl;
        if ((numbytes = sendto(sockfd, myPrice, strlen(myPrice), 0, p->ai_addr, p->ai_addrlen)) == -1) {
            perror("talker: sendto");
            exit(1);
        }
        std::this_thread::sleep_for(std::chrono::milliseconds(1000));
    }

    freeaddrinfo(servinfo);

    printf("talker: sent %d bytes to %s\n", numbytes, argv[1]);
    close(sockfd);

    return 0;
}

勾选听众：

/*
 ** listener.c -- a datagram sockets "server" demo
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>

#define MYPORT "4950"    // the port users will be connecting to

#define MAXBUFLEN 100

// get sockaddr, IPv4 or IPv6:
void *get_in_addr(struct sockaddr *sa)
{
    if (sa->sa_family == AF_INET) {
        return &(((struct sockaddr_in*)sa)->sin_addr);
    }

    return &(((struct sockaddr_in6*)sa)->sin6_addr);
}

int main(void)
{
    int sockfd;
    struct addrinfo hints, *servinfo, *p;
    int rv;
    int numbytes;
    struct sockaddr_storage their_addr;
    char buf[MAXBUFLEN];
    socklen_t addr_len;
    char s[INET6_ADDRSTRLEN];

    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC; // set to AF_INET to force IPv4
    hints.ai_socktype = SOCK_DGRAM;
    hints.ai_flags = AI_PASSIVE; // use my IP

    if ((rv = getaddrinfo(NULL, MYPORT, &hints, &servinfo)) != 0) {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
        return 1;
    }

    // loop through all the results and bind to the first we can
    for(p = servinfo; p != NULL; p = p->ai_next) {
        if ((sockfd = socket(p->ai_family, p->ai_socktype,
                             p->ai_protocol)) == -1) {
            perror("listener: socket");
            continue;
        }

        if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
            close(sockfd);
            perror("listener: bind");
            continue;
        }

        break;
    }

    if (p == NULL) {
        fprintf(stderr, "listener: failed to bind socket\n");
        return 2;
    }

    freeaddrinfo(servinfo);

    printf("listener: waiting to recvfrom...\n");

    addr_len = sizeof their_addr;

    while(1) {
        if ((numbytes = recvfrom(sockfd, buf, MAXBUFLEN-1 , 0,
                                 (struct sockaddr *)&their_addr, &addr_len)) == -1) {
            perror("recvfrom");
            exit(1);
        }

        printf("listener: got packet from %s\n",
               inet_ntop(their_addr.ss_family,
                         get_in_addr((struct sockaddr *)&their_addr),
                         s, sizeof s));
        printf("listener: packet is %d bytes long\n", numbytes);
        buf[numbytes] = '\0';
        printf("listener: packet contains \"%s\"\n", buf);
    }

    close(sockfd);

    return 0;
}

Answer 1

问题是侦听器中的绑定。您应该绑定到INADDR_ANY而不是特定的IP地址。

查看发件人发送的实际IP地址也很有趣。