I try to write the app to same thing like "Ping" in windows. I get problem that I can not receive the reply. In this app also has sniffing function. what happened : When I use "Ping" in windows, my sniffer can catch all the send/rev. When I use my app to send icmp to same address. I can catch what I send, but never rev the reply. When I use my app to send icmp to 127.0.0.1, I get nothing in sniffer. pls help me, thanks here is related code: (do i need any settings? like WSAIoctl and setsockopt) <code> RecvAddr.sin_family=AF_INET; RecvAddr.sin_port = htons(Port); RecvAddr.sin_addr.s_addr=inet_addr(DEFAULT_RECV_ADDR); icmp_socket=WSASocket(AF_INET, SOCK_RAW, IPPROTO_ICMP, NULL, 0, WSA_FLAG_OVERLAPPED); //initialise the icmp header ZeroMemory(buf,sizeof(buf)); int size=sizeof(buf); size=sizeof(ICMP); //icmp_icmp=*(ICMP *)buf; icmp_icmp.icmp_type= 8;//ICMP ECHO icmp_icmp.icmp_code=0; icmp_icmp.icmp_sequence=0; icmp_icmp.icmp_id=(WORD)GetCurrentProcessId(); icmp_icmp.icmp_timestamp=GetTickCount(); icmp_icmp.icmp_checksum=ICMPChecksum((WORD *)buf,(sizeof(ICMP)+32)); memcpy(buf,&icmp_icmp,sizeof(icmp_icmp)); //fill the payload with anything memset(&buf[sizeof(ICMP)], '@', 32); WORD ICMPClass::ICMPChecksum(WORD * data, int len) { DWORD cksum=0; while(len>1) { cksum+=*data++; len-=sizeof(WORD); } if(len) { cksum+= *(WORD*)data; } cksum=(cksum >>16)+(cksum &0xffff); cksum+=(cksum >> 16); return (WORD)(~cksum); } In IO class DataBuf.len=ICMP_SEND_BUFFER_SIZE; DataBuf.buf=buf; overlapEventList[ICMP_WRITE]=WSACreateEvent(); overlapList[ICMP_WRITE].hEvent=overlapEventList[ICMP_WRITE]; result = WSASendTo(icmp_socket, &DataBuf, 1,&BytesSent, Flags, (SOCKADDR *) icmp->GetRecvAddr(), sizeof(SOCKADDR), &overlapList[ICMP_WRITE], NULL); </code>

Assuming the above is implemented correctly, the problem might be with the ISP. Many filter out ICMP traffic. UDP is sometimes used instead. TCP SYN is another option.

Quote:Original post by Antheus
Assuming the above is implemented correctly, the problem might be with the ISP. Many filter out ICMP traffic. UDP is sometimes used instead. TCP SYN is another option.

I said when I use windows "Ping" app, it works. it means nothing to do with ISP.

I found the problem. I did the data(catched by sniffer) compare, it turns out the checksum is wrong.

just for sharing, the correct code should be

<code>

//initialise the icmp header
ZeroMemory(buf,sizeof(buf));
int size=sizeof(buf);
size=sizeof(ICMP);
icmp_icmp=(ICMP *)buf;
icmp_icmp->icmp_type= 8;//ICMP ECHO
icmp_icmp->icmp_code=0;
icmp_icmp->icmp_sequence=0;
icmp_icmp->icmp_id=(WORD)GetCurrentProcessId();
icmp_icmp->icmp_checksum = 0;
icmp_icmp->icmp_timestamp=GetTickCount();

//memcpy(buf,icmp_icmp,sizeof(icmp_icmp));
//fill the payload with anything
memset(&buf[sizeof(ICMP)], '@', 32);

icmp_icmp->icmp_checksum=ICMPChecksum((WORD *)buf,(sizeof(ICMP)+32));

<\code>