Приём сырых сокетов

    //Create a raw socket
    int s = socket (PF_INET, SOCK_RAW, IPPROTO_TCP);
 
    if(s == -1)
    {
        //socket creation failed, may be because of non-root privileges
        ui->textBrowser->append("Failed to create socket");
    }
 
    //Datagram to represent the packet
    char datagram[4096] , source_ip[32] , *data , *pseudogram;
 
    //zero out the packet buffer
    memset (datagram, 0, 4096);
 
    //IP header
    struct iphdr *iph = (struct iphdr *) datagram;
 
    //TCP header
    struct tcphdr *tcph = (struct tcphdr *) (datagram + sizeof (struct ip));
    struct sockaddr_in sin;
    struct pseudo_header psh;
 
    //Data part
    data = datagram + sizeof(struct iphdr) + sizeof(struct tcphdr);
    strcpy(data , "Request for new MAC");
 
    //some address resolution
    ui->textBrowser->append("Request will be send from IP  "+getCurrentIp().toAscii() + "\n");
    strcpy(source_ip , getCurrentIp().toAscii());
    sin.sin_family = AF_INET;
    sin.sin_port = htons(4242);
    sin.sin_addr.s_addr = inet_addr(_SERVER_IP);
 
    //Fill in the IP Header
    iph->ihl = 5;
    iph->version = 4;
    iph->tos = 0;
    iph->tot_len = sizeof (struct iphdr) + sizeof (struct tcphdr) + strlen(data);
    iph->id = htonl (54321);    //Id of this packet
    iph->frag_off = 0;
    iph->ttl = 255;
    iph->protocol = IPPROTO_TCP;
    iph->check = 0;     //Set to 0 before calculating checksum
    iph->saddr = inet_addr ( source_ip );
    iph->daddr = sin.sin_addr.s_addr;
 
    //Ip checksum
    iph->check = csum ((unsigned short *) datagram, iph->tot_len);
 
    //TCP Header
    tcph->source = htons (4242);
    tcph->dest = htons (4242);
    tcph->seq = 0;
    tcph->ack_seq = 0;
    tcph->doff = 5; //tcp header size
    tcph->fin=0;
    tcph->syn=1;
    tcph->rst=0;
    tcph->psh=0;
    tcph->ack=0;
    tcph->urg=0;
    tcph->window = htons (5840);    /* maximum allowed window size */
    tcph->check = 0;    //leave checksum 0 now, filled later by pseudo header
    tcph->urg_ptr = 0;
 
    //Now the TCP checksum
    psh.source_address = inet_addr( source_ip );
    psh.dest_address = sin.sin_addr.s_addr;
    psh.placeholder = 0;
    psh.protocol = IPPROTO_TCP;
    psh.tcp_length = htons(sizeof(struct tcphdr) + strlen(data) );
 
    int psize = sizeof(struct pseudo_header) + sizeof(struct tcphdr) + strlen(data);
    pseudogram = (char*)malloc(psize);
 
    memcpy(pseudogram , (char*) &psh , sizeof (struct pseudo_header));
    memcpy(pseudogram + sizeof(struct pseudo_header) , tcph , sizeof(struct tcphdr) + strlen(data));
 
    tcph->check = csum( (unsigned short*) pseudogram , psize);
 
    //IP_HDRINCL to tell the kernel that headers are included in the packet
    int one = 1;
    const int *val = &one;
 
    if (setsockopt (s, IPPROTO_IP, IP_HDRINCL, val, sizeof (one)) < 0)
    {
        ui->textBrowser->append("!!Error setting IP_HDRINCL!! \n");
    }
 
    //Send the packet
    if (sendto (s, datagram, iph->tot_len , 0, (struct sockaddr *) &sin, sizeof (sin)) < 0)
    {
        ui->textBrowser->append("sendto failed");
    }
    //Data send successfully
    else
    {
        ui->textBrowser->append(QString("Packet Send. Length : %1 \n").arg(iph->tot_len));
    }

    int sockfd;
    struct addrinfo hints, *res;
 
    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC; // use IPv4 or IPv6, whichever
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_PASSIVE; // fill in my IP for me
    getaddrinfo(NULL, "3490", &hints, &res);
    // make a socket:
    sockfd = socket(AF_INET,SOCK_RAW,IPPROTO_TCP);
    // bind it to the port we passed in to getaddrinfo():
    bind(sockfd, res->ai_addr, res->ai_addrlen);
    
    char buff[70] = "";
    for(int i=0;i<5;i++){
    recv(sockfd,buff,sizeof(buff),0);
    qDebug()<< buff;
    }