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我写的代码如下。该程序将尽可能多地向远程机器发送 TCP 数据包。sendto 函数成功，但我无法检测到来自本地或远程机器的数据包。它出什么问题了？我使用 Wireshark 来检测数据包。

//raw tcp packet crafter

#include "stdio.h"
#include "winsock2.h"
#include "ws2tcpip.h"  //IP_HDRINCL is here
#include "conio.h"

#pragma comment(lib,"ws2_32.lib")  //winsock 2.2 library

typedef struct ip_hdr
{
    unsigned char  ip_header_len:4;  // 4-bit header length (in 32-bit words) normally=5 (Means 20 Bytes may be 24 also)
    unsigned char  ip_version   :4;  // 4-bit IPv4 version
    unsigned char  ip_tos;           // IP type of service
    unsigned short ip_total_length;  // Total length
    unsigned short ip_id;            // Unique identifier 

    unsigned char  ip_frag_offset   :5;        // Fragment offset field

    unsigned char  ip_more_fragment :1;
    unsigned char  ip_dont_fragment :1;
    unsigned char  ip_reserved_zero :1;

    unsigned char  ip_frag_offset1;    //fragment offset

    unsigned char  ip_ttl;           // Time to live
    unsigned char  ip_protocol;      // Protocol(TCP,UDP etc)
    unsigned short ip_checksum;      // IP checksum
    unsigned int   ip_srcaddr;       // Source address
    unsigned int   ip_destaddr;      // Source address
}   IPV4_HDR, *PIPV4_HDR, FAR * LPIPV4_HDR;


// TCP header
typedef struct tcp_header 
{ 
    unsigned short source_port;  // source port 
    unsigned short dest_port;    // destination port 
    unsigned int   sequence;     // sequence number - 32 bits 
    unsigned int   acknowledge;  // acknowledgement number - 32 bits 

    unsigned char  ns   :1;          //Nonce Sum Flag Added in RFC 3540.
    unsigned char  reserved_part1:3; //according to rfc
    unsigned char  data_offset:4;    /*The number of 32-bit words in the TCP header. 
                                       This indicates where the data begins. 
                                       The length of the TCP header is always a multiple 
                                       of 32 bits.*/

    unsigned char  fin  :1;      //Finish Flag
    unsigned char  syn  :1;      //Synchronise Flag
    unsigned char  rst  :1;      //Reset Flag
    unsigned char  psh  :1;      //Push Flag 
    unsigned char  ack  :1;      //Acknowledgement Flag 
    unsigned char  urg  :1;      //Urgent Flag

    unsigned char  ecn  :1;      //ECN-Echo Flag
    unsigned char  cwr  :1;      //Congestion Window Reduced Flag

    ////////////////////////////////

    unsigned short window;  // window 
    unsigned short checksum;  // checksum 
    unsigned short urgent_pointer;  // urgent pointer 
}   TCP_HDR , *PTCP_HDR , FAR * LPTCP_HDR , TCPHeader , TCP_HEADER;

int main()
{
    char host[100],buf[1000],*data=NULL,source_ip[20]; //buf is the complete packet
    SOCKET s;
    int k=1;

    IPV4_HDR *v4hdr=NULL;
    TCP_HDR  *tcphdr=NULL;

    int payload=512 , optval;
    SOCKADDR_IN dest;

    //Initialise Winsock
    WSADATA wsock;
    printf("\nInitialising Winsock...");
    if (WSAStartup(MAKEWORD(2,2),&wsock) != 0)
    {
        fprintf(stderr,"WSAStartup() failed");
        exit(EXIT_FAILURE); 
    } 
    printf("Initialised successfully.");
    ////////////////////////////////////////////////

    //Create Raw TCP Packet
    printf("\nCreating Raw TCP Socket...");
    if((s = socket(AF_INET, SOCK_RAW, IPPROTO_IP))==SOCKET_ERROR)
    {
        printf("Creation of raw socket failed.");
        return 0;
    }
    printf("Raw TCP Socket Created successfully.");
    ////////////////////////////////////////////////

    //Put Socket in RAW Mode.
    printf("\nSetting the socket in RAW mode...");
    if(setsockopt(s, IPPROTO_IP, IP_HDRINCL, (char *)&optval, sizeof(optval))==SOCKET_ERROR)
    {
        printf("failed to set socket in raw mode.");
        return 0;
    }
    printf("Successful.");
    ////////////////////////////////////////////////

    dest.sin_family = AF_INET;
    dest.sin_port   = htons(81);  //your destination port
    dest.sin_addr.s_addr = inet_addr("192.168.1.230");
    /////////////////////////////////////////////////


    v4hdr = (IPV4_HDR *)buf;  //lets point to the ip header portion
    v4hdr->ip_version=4;
    v4hdr->ip_header_len=5;
    v4hdr->ip_tos    = 0;
    v4hdr->ip_total_length = htons ( sizeof(IPV4_HDR) + sizeof(TCP_HDR) + payload );
    v4hdr->ip_id     = 0;//htons(2);
    v4hdr->ip_frag_offset = 0;
    v4hdr->ip_frag_offset1 = 0;
    v4hdr->ip_reserved_zero = 0;
    v4hdr->ip_dont_fragment = 1;
    v4hdr->ip_more_fragment = 0;
    v4hdr->ip_ttl    = 8;
    v4hdr->ip_protocol = IPPROTO_TCP;
    v4hdr->ip_srcaddr  = inet_addr("192.168.1.232");
    v4hdr->ip_destaddr = inet_addr(inet_ntoa(dest.sin_addr));
    v4hdr->ip_checksum = 0;

    tcphdr = (TCP_HDR *)&buf[sizeof(IPV4_HDR)]; //get the pointer to the tcp header in the packet

    tcphdr->source_port = htons(123);
    tcphdr->dest_port = htons(81);

    tcphdr->cwr=0;
    tcphdr->ecn=1;
    tcphdr->urg=0;
    tcphdr->ack=0;
    tcphdr->psh=0;
    tcphdr->rst=1;
    tcphdr->syn=0;
    tcphdr->fin=0;
    tcphdr->ns=1;

    tcphdr->checksum = 0;


    // Initialize the TCP payload to some rubbish
    data = &buf[sizeof(IPV4_HDR) + sizeof(TCP_HDR)];
    memset(data, '^', payload);


    printf("\nSending packet...\n");

    while(!_kbhit())
    {
        printf("  %d  packets send\r",k++);
        if((sendto(s , buf , sizeof(IPV4_HDR)+sizeof(TCP_HDR) + payload, 0,
               (SOCKADDR *)&dest, sizeof(dest)))==SOCKET_ERROR)
        {

        printf("Error sending Packet : %d",WSAGetLastError());
        break;
        }
    }


    return 0;
}
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