Question

以下代码是用于发送ICMP回应请求并接收回复的程序。

/*
    Forgive my lack of error handling :)
*/
SOCKET ASOCKET = INVALID_SOCKET;
struct sockaddr saddr;
struct sockaddr_in *to = (struct sockaddr_in *) &saddr;
struct sockaddr_in from;
int fromsize = sizeof(from);
std::string ip = "[arbitrary ip address]";

struct ICMP {
    USHORT type;
    USHORT code;
    USHORT cksum;
    USHORT id;
    USHORT seq;
}*_ICMP;

char sendBuffer[sizeof(struct ICMP)];
char recvBuffer[256];

WSADATA wsaData;
WSAStartup(MAKEWORD(2, 2), &wsaData);

memset(&saddr, NULL, sizeof(saddr));
ASOCKET = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);

//  Configure timeout
DWORD timeoutmilsec = 3000;
setsockopt(ASOCKET, SOL_SOCKET, SO_RCVTIMEO, (char *)&timeoutmilsec, sizeof(timeoutmilsec));

to->sin_family = AF_INET;
inet_pton(AF_INET, ip.c_str(), &(to->sin_addr));

_ICMP = new ICMP();

_ICMP->type = 8;
_ICMP->code = 0;
_ICMP->cksum = 0;
_ICMP->id = rand();
_ICMP->seq++;
// I have omitted my declaration of checksum() for simplicity
_ICMP->cksum = checksum((u_short *)_ICMP, sizeof(struct ICMP));

memcpy(sendBuffer, _ICMP, sizeof(struct ICMP));

if (sendto(ASOCKET, sendBuffer, sizeof(sendBuffer), NULL, (sockaddr *)&saddr, sizeof(saddr)) == SOCKET_ERROR)
{
    printf("sendto() failed with error: %u\n", WSAGetLastError());
    return false;
}

if (recvfrom(ASOCKET, recvBuffer, sizeof(recvBuffer), NULL, (sockaddr *)&from, &fromsize) == SOCKET_ERROR)
{
    if (WSAGetLastError() == TIMEOUTERROR)
    {
        printf("Timed out\n\n");
        return false;
    }

    printf("recvfrom() failed with error: %u\n", WSAGetLastError());
    return false;
}

我的问题是我的recvfrom()来电没有收到任何数据并返回TIMEOUTERROR（10060），尽管ping 已经被回复（Wireshark捕获请求并回复发送）。 sendto()有效但recvfrom()行为奇怪，我无法弄清问题是什么。

我觉得有趣的是recvfrom()仅在网关告诉我主机无法访问时才会收到数据;如果主机可以访问并且响应了ping，它就不会获胜。

Answer 1

问题在于<client> <endpoint address="http://localhost:1001/Services/Service1.svc" behaviorConfiguration="webBehavior" binding="webHttpBinding" contract="MainService.IService1" /> </client>。

ICMP的

struct ICMP和type应为code。

ICMP的标头应为8字节，但unsigned char的大小为10字节。

所以应该改为：

struct ICMP

Answer 2

事实证明，我的防火墙阻止响应的整个时间。我的代码中唯一的错误是我的ICMP结构的大小（由cshu提到）。

感谢所有人的帮助。

RAW ICMP套接字：recvfrom（）没有收到任何数据

2 个答案: