setsockopt失败并返回-1

Question

我试图运行一个演示使用GSOAP的发现功能的示例。不幸的是，我似乎在setsockopt上得到了一个-1为什么可能会发生什么建议？错误号是无效的参数。

const char* host = "127.0.0.1"; 
int port = 3702; 
const int _metadataVersion = 1; 
const char* _xaddr="http://localhost/service"; 
const char* _type="\"http://schemas.xmlsoap.org/ws/2006/02/devprof\":device"; 
const char* _scope="scope"; 
const char* _endpoint="urn"; 

int main(int argc, char** argv) 
{ 
    struct soap* serv = soap_new1(SOAP_IO_UDP); 
    serv->bind_flags=SO_REUSEADDR; 
    if (!soap_valid_socket(soap_bind(serv, NULL, port, 1000))) 
    { 
     std::cout << "Error in Bind \n"; 
     soap_print_fault(serv, stderr); 
     exit(1); 
    } 
    ip_mreq mcast; 
    mcast.imr_multiaddr.s_addr = inet_addr(host); 
    mcast.imr_interface.s_addr = htonl(INADDR_ANY); 
    int res = setsockopt(serv->master, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mcast, sizeof(mcast)); 
     std::cout << "setsockopt returned " << res << "\n"; 
     if(res < 0) 
    //if (setsockopt(serv->master, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mcast, sizeof(mcast))<0) 
    { 
     std::cout << "group membership failed:" << strerror(errno) << std::endl; //The error no is invalid Argument 
     exit(1);   
    } 

    sendHello(); 
    mainloop(serv); 

    signal(SIGINT, &sighandler); 
    while (!stop) 
    { 
     mainloop(serv); 
    } 

    sendBye(); 
    mainloop(serv); 

    return 0; 
} 

Answer 1

的host = "127.0.0.1"，它应该是一个有效的multicast address，从224.0.0.0到239.255.255.255。

---

这里有三种方法可以帮助你分析这个问题。

• 确保host的地址是一个有效的多播地址。

• 使用ifconfig wlan0或任何其他接口，您可以检查是否已正确启用MultiCast。

• 用下面的代码检查组播地址是否正确。

  struct sockaddr_in sa; 
  if (-1 == inet_pton(AF_INET, host/*such as 192.0.2.33*/, &sa.sin_addr)) 
      error("cannot set multicast address: %s\n", strerror(errno)); 
  memcpy(&mreq.imr_multiaddr.s_addr, (void*)&sa.sin_addr, sizeof(struct in_addr)); 
  mreq.imr_interface.s_addr = htonl(INADDR_ANY);