Linux中的INADDR_ANY与Windows套接字编程之间的区别
我的Winsock Delphi应用程序应该在所有网络接口上侦听多播UDP / IP流.它正常收听,直到我在具有不同网络适配器优先级顺序的另一台PC上尝试它.
然后我开始研究问题,并在一些论坛上发现INADDR_ANY(或0.0.0.0)在Windows和Linux中有不同的含义: >在Linux it means “listen on all interfaces”中和发送 – 通过默认接口发送 你能否证实或否认这一点? 如何在所有界面上真实收听? 这是我的一小段代码: TMulticastListener = class(TThread) private mreq: ip_mreq; ............ end; constructor TMulticastListener.Create; var err: Integer; wData: WsaData; reuse: Integer; begin inherited Create(true); err := WSAStartup(MAKEWORD(2,2),wData); if err = SOCKET_ERROR then begin // Tell the user that we could not find a usable Winsock DLL perror('WSAStartup'); Exit; end; // create what looks like an ordinary UDP socket fd := socket(AF_INET,SOCK_DGRAM,0); if fd = INVALID_SOCKET then begin perror('socket'); Exit; end; reuse := 1; // allow multiple sockets to use the same PORT number if (setsockopt(fd,SOL_SOCKET,SO_REUSEADDR,Pointer(@reuse),SizeOf(reuse)) < 0) then begin perror('Reusing ADDR failed'); Exit; end; // set up destination address FillChar(addr,sizeof(addr),0); addr.sin_family := AF_INET; addr.sin_addr.s_addr := htonl(INADDR_ANY); // N.B.: differs from sender addr.sin_port := htons(HELLO_PORT); // bind to receive address if (bind(fd,addr,sizeof(addr)) < 0) then begin perror('bind'); Exit; end; // use setsockopt() to request that the kernel join a multicast group mreq.imr_multiaddr.s_addr := inet_addr(HELLO_GROUP); mreq.imr_interface.s_addr := htonl(INADDR_ANY); //inet_addr('0.0.0.0'); if (setsockopt(fd,IPPROTO_IP,IP_ADD_MEMBERSHIP,@mreq,sizeof(mreq)) < 0) then begin perror('setsockopt'); Exit; end; end; 解决方法
在使用INADDR_ANY时,Windows和Linux实际上表现相同.这里的混淆是因为您提供的两个链接正在不同的上下文中使用.
使用bind函数绑定到地址/端口时,指定INADDR_ANY意味着套接字将能够从任何接口接收给定端口上的数据包.但是,这样做不会设置有关多播的任何内容. 在对setsockopt的IP_ADD_MEMBERSHIP调用的上下文中,将接口设置为INADDR_ANY将使系统在默认网络接口上加入给定的多播组. 您提供的Linux链接指的是bind,而Windows链接指的是setsockopt和IP_ADD_MEMBERSHIP. 如果要在所有接口上加入组播组,则需要检索系统上的接口列表并加入每个接口.在Windows上, 以下是如何在C中使用GetAdaptersAddresses()函数的示例: struct iflist { char name[50]; struct sockaddr_in sin; int isloopback; int ismulti; int ifidx; }; void getiflist(struct iflist *list,int *len) { IP_ADAPTER_ADDRESSES *head,*curr; IP_ADAPTER_UNICAST_ADDRESS *uni; char *buf; int buflen,err,i; buflen = 100000; buf = calloc(buflen,1); head = (IP_ADAPTER_ADDRESSES *)buf; if ((err = GetAdaptersAddresses(AF_UNSPEC,NULL,head,&buflen)) != ERROR_SUCCESS) { char errbuf[300]; FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM,errbuf,sizeof(errbuf),NULL); printf("GetAdaptersAddresses failed: (%d) %s",errbuf); free(buf); return; } for (*len = 0,curr = head; curr; curr = curr->Next) { if (curr->IfType == IF_TYPE_TUNNEL) continue; for (uni = curr->FirstUnicastAddress; uni; uni = uni->Next) { if (curr->OperStatus == IfOperStatusUp) { memset(&list[*len],sizeof(struct iflist)); strncpy(list[*len].name,(char *)curr->AdapterName,sizeof(list[i].name) - 1); memcpy(&list[*len].sin,uni->Address.lpSockaddr,uni->Address.iSockaddrLength); list[*len].isloopback = (curr->IfType == IF_TYPE_SOFTWARE_LOOPBACK); list[*len].ismulti = ((curr->Flags & IP_ADAPTER_NO_MULTICAST) == 0); if (uni->Address.lpSockaddr->sa_family == AF_INET6) { list[*len].ifidx = curr->Ipv6IfIndex; } else { list[*len].ifidx = curr->IfIndex; } (*len)++; } } } free(buf); } (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |