在macOS Big Sur上接收UDP多播

m

我知道这可能是接收UDP多播消息的第10.000个问题。但是,半年前我已经开始使用它了。我从http://www.cs.tau.ac.il/~eddiea/samples/Multicast/multicast-listen.c.html获得的以下代码段(按较小的更改:bind-ip更改为IPADDR_ANY)按预期工作在我升级到macOS Big Sur之前。

/**************************************************************/
/* Multicast listener (server)                                */
/*                                                            */
/* Activation using: {program name} {Multicast IP} {port}     */
/*   {program name} - This program name                       */
/*   {Multicast IP} - The IP address to listen to (Class D)   */
/*   {port} - The port hnumber to listen on                   */
/*                                                            */
/* This is free software released under the GPL license.      */
/* See the GNU GPL for details.                               */
/*                                                            */
/* (c) Juan-Mariano de Goyeneche. 1998, 1999.                 */
/**************************************************************/


#include <stdio.h>          /* printf(), snprintf() */
#include <stdlib.h>         /* strtol(), exit() */
#include <sys/types.h>
#include <sys/socket.h>     /* socket(), setsockopt(), bind(), recvfrom(), sendto() */
#include <errno.h>          /* perror() */
#include <netinet/in.h>     /* IPPROTO_IP, sockaddr_in, htons(), htonl() */
#include <arpa/inet.h>      /* inet_addr() */
#include <unistd.h>         /* fork(), sleep() */
#include <sys/utsname.h>    /* uname() */
#include <string.h>         /* memset() */

#define MAXLEN 1024


int main(int argc, char* argv[])
{
  u_char no = 0;
  u_int yes = 1;      /* Used with SO_REUSEADDR.
                             In Linux both u_int */
  /* and u_char are valid. */
  int send_s, recv_s;     /* Sockets for sending and receiving. */
  u_char ttl;
  struct sockaddr_in mcast_group;
  struct ip_mreq mreq;
  struct utsname name;
  int n;
  socklen_t socklen;
  struct sockaddr_in from;
  char message [MAXLEN+1];

  if (argc != 3) {
    fprintf(stderr, "Usage: %s mcast_group port\n", argv[0]);
    exit(1);
  }

  memset(&mcast_group, 0, sizeof(mcast_group));
  mcast_group.sin_family = AF_INET;
  mcast_group.sin_port = htons((unsigned short int)strtol(argv[2], NULL, 0));
  mcast_group.sin_addr.s_addr = htonl(INADDR_ANY);

  if ( (recv_s=socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
    perror ("recv socket");
    exit(1);
  }

  if (setsockopt(recv_s, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(yes)) < 0) {
    perror("reuseaddr setsockopt");
    exit(1);
  }

  if (bind(recv_s, (struct sockaddr*)&mcast_group, sizeof(mcast_group)) < 0) {
    perror ("bind");
    exit(1);
  }

  struct in_addr sin;
  inet_pton(AF_INET, argv[1], &sin);
  /* Preparatios for using Multicast */
  mreq.imr_multiaddr = sin;
  mreq.imr_interface.s_addr = 0;

  /* Tell the kernel we want to join that multicast group. */
  if (setsockopt(recv_s, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0) {
    perror ("add_membership setsockopt");
    exit(1);
  }

  for (;;) {
    socklen=sizeof(from);
    if ( (n=recvfrom(recv_s, message, MAXLEN, 0,
                     (struct sockaddr*)&from, &socklen)) < 0) {
      perror ("recv");
      exit(1);
    }
    message[n] = '\0'; /* null-terminate string */
    printf("%s: Received message from %s, size=%d !!\n",
           name.nodename,
           inet_ntoa(from.sin_addr), n);
    printf("\t%s \n", message);
  }
}

现在,我尝试使其再次运行,但找不到任何无法运行的原因。Big Sur中的某些政策是否发生了变化,这是一些权限错误?我已经以root用户身份运行应用程序,sudo ./multicast-listen 239.255.255.250 1900但这也不起作用。我正在尝试接收SSDP软件包。

m

因此,@ CraigEstey的评论使我得出结论,认为它必须与防火墙有关。确实,这是一个简单的防火墙问题。Settings-> Security-> Firewall->中,Firewall Options...您必须禁用Block all incoming connections和禁用隐形模式。现在,我将按预期收到所有SSDP软件包。

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