[C(++)] voor dummies

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// include ook de lib (D:\IDE\MinGW\lib\libws2_32.a)

#include <iostream>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <string>

/* ICMP codes */
#define ICMP_ECHO_REPLY 0
#define ICMP_DEST_UNREACH 3
#define ICMP_TTL_EXPIRE 11
#define ICMP_ECHO_REQUEST 8

struct Error{
    std::string _ERROR;
    Error(std::string error):_ERROR(error){}
};
// The IP header
struct IPHeader {
    char h_len:4;           // Length of the header in dwords
    char version:4;         // Version of IP
    char tos;               // Type of service
    unsigned short total_len;       // Length of the packet in dwords
    unsigned short ident;           // unique identifier
    unsigned short flags;           // Flags
    char ttl;               // Time to live
    char proto;             // Protocol number (TCP, UDP etc)
    unsigned short checksum;        // IP checksum
    unsigned long source_ip;
    unsigned long dest_ip;
};
// ICMP header
struct ICMPHeader {
    char type;          // ICMP packet type
    char code;          // Type sub code
    unsigned short checksum;
    unsigned short id;
    unsigned short seq;
};

unsigned short ip_checksum(unsigned short* buffer, int size){
    unsigned long cksum = 0;

    // Sum all the words together, adding the final byte if size is odd
    while (size > 1) {
        cksum += *buffer++;
        size -= sizeof(unsigned short);
    }
    if (size) {
        cksum += *(unsigned char*)buffer;
    }

    // Do a little shuffling
    cksum = (cksum >> 16) + (cksum & 0xffff);
    cksum += (cksum >> 16);

    // Return the bitwise complement of the resulting mishmash
    return (unsigned short)(~cksum);
}
unsigned long FindHostIP(const char *pServerName){
    std::cout << "Looking up host... ";
    HOSTENT *pHostent;

    // Get hostent structure for hostname:
    if(!(pHostent = gethostbyname(pServerName))){
        std::cout << "Failed!\n";
        throw Error("Lookup Failed!");
    }

    // Extract primary IP address from hostent structure:
    if(pHostent->h_addr_list && pHostent->h_addr_list[0]){
        std::cout << "Done.\n";
        return *reinterpret_cast<unsigned long*>(pHostent->h_addr_list[0]);
    }
    return 0;
}

unsigned short CalcChecksum(char *pBuffer,int nLen){
    //Checksum for ICMP is calculated in the same way as for
    //IP header

    //This code was taken from: http://www.netfor2.com/ipsum.htm

    unsigned short nWord;
    unsigned int nSum = 0;
    int i;

    //Make 16 bit words out of every two adjacent 8 bit words in the packet
    //and add them up
    for(i = 0; i < nLen; i = i + 2){
        nWord =((pBuffer [i] << 8)& 0xFF00) + (pBuffer [i + 1] & 0xFF);
        nSum = nSum + (unsigned int)nWord;
    }

    //Take only 16 bits out of the 32 bit sum and add up the carries
    while (nSum >> 16){
        nSum = (nSum & 0xFFFF) + (nSum >> 16);
    }

    //One's complement the result
    nSum = ~nSum;

    return ((unsigned short) nSum);
}
bool ValidateChecksum(char *pBuffer,int nLen){
    unsigned short nWord;
    unsigned int nSum = 0;
    int i;

    //Make 16 bit words out of every two adjacent 8 bit words in the packet
    //and add them up
    for(i = 0; i < nLen; i = i + 2)    {
        nWord =((pBuffer [i] << 8)& 0xFF00) + (pBuffer [i + 1] & 0xFF);
        nSum = nSum + (unsigned int)nWord;
    }

    //Take only 16 bits out of the 32 bit sum and add up the carries
    while(nSum >> 16){
        nSum = (nSum & 0xFFFF) + (nSum >> 16);
    }

    //To validate the checksum on the received message we don't complement the sum
    //of one's complement
    //One's complement the result
    //nSum = ~nSum;

    //The sum of one's complement should be 0xFFFF
    return((unsigned short)nSum == 0xFFFF);
}
bool Initialize(){
    //Initialize WinSock
    WSADATA wsaData;

    if (WSAStartup (MAKEWORD (2, 2), &wsaData) == SOCKET_ERROR){
        throw Error("An error occured in WSAStartup operation");
        return false;
    }

    return true;
}
bool UnInitialize(){
    //Cleanup
    if(WSACleanup() == SOCKET_ERROR){
        std::cerr << "\nAn error occured in WSACleanup operation\n";
        return false;
    }

    return true;
}

int main (int argc, char* argv[]){
    if(argc < 2 || argc > 2){
        std::cout << argv[0] << ' ' << "[IPadres]\n";
        return 0;
    }
    unsigned MessageSize = 32;


    try{
        Initialize();

        std::cout << "Creating Socket... ";
        SOCKET Sock = INVALID_SOCKET;
        if((Sock = socket(AF_INET,SOCK_RAW,IPPROTO_ICMP)) == INVALID_SOCKET){
            std::cout << "Failed!\n";
            throw Error("Invalid Socket");
        }
        std::cout << "Done.\n";
        sockaddr_in dest; // Destination address to send the ICMP
        dest.sin_addr.S_un.S_addr = FindHostIP(argv[1]);
        dest.sin_family = AF_INET;
        SYSTEMTIME timeSend,timeRecv;
        fd_set fdRead;
        int result = 0;

        /* Create the message buffer */
        char* SendBuff = new char[sizeof(ICMPHeader)+MessageSize];
        ICMPHeader sendHdr;
        sendHdr.type = ICMP_ECHO_REQUEST;
        sendHdr.code = 0;
        sendHdr.checksum = 0; // checksum is calculated later on
        sendHdr.seq = 0; // this is the counter to keep track of the messages (in a loop this value will go up)

        memcpy(SendBuff,&sendHdr,sizeof(sendHdr));
        memset(SendBuff+sizeof(sendHdr),'x',MessageSize); // fills the rest with x

        sendHdr.checksum = htons(CalcChecksum(SendBuff,sizeof(ICMPHeader)+MessageSize));
        // copy the message header back into the buffer
        memcpy(SendBuff,&sendHdr,sizeof(sendHdr));

        std::cout << "Sending... ";
        result = sendto(Sock,SendBuff,sizeof(ICMPHeader)+MessageSize,0,(sockaddr*)&dest,sizeof(dest));
        ::GetSystemTime(&timeSend); // Save's the sending time
        if(result == SOCKET_ERROR){
            delete[] SendBuff;
            std::cout << "Failed!\n";
            throw Error("Can't Send\n");
        }
        std::cout << "Done.\n";

        FD_ZERO(&fdRead);
        FD_SET(Sock,&fdRead);
        timeval timeInterval = {0, 0};
        timeInterval.tv_usec = 5 * 1000; // timeout = 5 sec
        if((result = select(0,&fdRead,0,0,&timeInterval)) == SOCKET_ERROR){
            delete[] SendBuff;
            throw Error("Occured at select operation");
        }
        if(result >0 && FD_ISSET(Sock,&fdRead)){
            std::cout << "Receiving... ";
            char *RecvBuff = new char[1500]; // allocate recv buffer
            if((result = recvfrom(Sock,RecvBuff,1500,0,0,0)) == SOCKET_ERROR){
                delete[] SendBuff;
                delete[] RecvBuff;
                std::cout << "Failed!\n";
                throw Error("Can't receive");
            }
            ::GetSystemTime(&timeRecv); // Get response time
            std::cout << "Done.\n";

            /*construct IcMP hader and message out of response */
            ICMPHeader recvHdr;
            char *ICMPBuff = RecvBuff + sizeof(IPHeader); // skip the ip header and go to ICMP message
            int ICMPMsgLen = result - sizeof(IPHeader);

            memcpy(&recvHdr,ICMPBuff,sizeof(recvHdr)); // constructs the ICMP header

            IPHeader IPHdr;
            memcpy(&IPHdr,RecvBuff,sizeof(IPHdr));

            // check if the response is the right reply and if the checksum is correct
            if(recvHdr.type == 0 && ValidateChecksum(ICMPBuff,ICMPMsgLen) && recvHdr.id == sendHdr.id && recvHdr.seq == recvHdr.seq){
                // all is ok
                int Sec = timeRecv.wSecond - timeSend.wSecond;
                if(Sec < 0)
                    Sec+=60;
                int MilliSec = abs(timeRecv.wMilliseconds-timeSend.wMilliseconds);
                int RoundTripTime = abs(Sec*1000-MilliSec);
                std::cout << "Reply from " << argv[1] << ": bytes = " << result-sizeof(ICMPHeader)-sizeof(IPHeader)
                          << ", time = " << RoundTripTime << "ms, TTL = " << (int)IPHdr.ttl << '\n';
            }
            else
                std::cout << "The echo reply is not correct!\n";

            delete[] RecvBuff;
        }
        else{
            std::cout << "Request timed out.\n";
            std::cout << result; // temp
        }
        delete[] SendBuff;
    }
    catch(Error(e)){
        std::cout << "\nERROR!\n";
        std::cout << e._ERROR << '\n';

        UnInitialize();
        return -1;
    }

    if(UnInitialize() == false)
        return -1;
    return 0;
}