问题描述
我知道这可能是接收 UDP 多播消息的第 10.000 个问题。但是,我已经在半年前开始工作了。在我升级到 macOS Big Sur 之前,我从 http://www.cs.tau.ac.il/~eddiea/samples/Multicast/multicast-listen.c.html 获得的以下代码段(稍作更改:绑定 ip 已更改为 IPADDR_ANY
)按预期工作。
/**************************************************************/
/* 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,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,(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);
}
}
现在我尝试让它再次运行,但我找不到任何不再起作用的原因。
Big Sur 的某些政策是否发生了变化,这是一些权限错误吗?我已经使用 sudo ./multicast-listen 239.255.255.250 1900
以 root 身份运行应用程序,但这也不起作用。我正在尝试接收 SSDP 包。
解决方法
所以@CraigEstey 的评论让我得出结论,它必须对防火墙做些什么。事实上,这是一个简单的防火墙问题。在 Settings
-> Security
-> Firewall
-> Firewall Options...
中,您必须禁用 Block all incoming connections
并禁用隐身模式。现在我按预期收到了所有 SSDP 包。