Folgeder Code sollte ein Raw Socket unter XP (nicht SP2) erstellen.
Er lässt sich mit gcc kompilieren, aber ich bekomme dann immer:

sendto() No Error

Und zwar bei:

if(sendto(s, buffer, ntohs(ip->total_len ), 0, (struct sockaddr*)&to, sizeof(to))==-1){ 
        perror("sendto() error"); 
    }

Und Paket wird keins verschickt! Was ist das Problem?

// includes 
#include <winsock2.h> 
#include <ws2tcpip.h> 
#include <windows.h> 
#include <stdio.h> 

// header 
struct iphdr { 
    unsigned int    len:4; 
    unsigned int    ver:4; 
    unsigned char     tos; 
    unsigned short     total_len; 
    unsigned short     ident; 
    unsigned short     frag_and_flags; 
    unsigned char     ttl; 
    unsigned char     proto; 
    unsigned short     checksum; 
    unsigned int     sourceIP; 
    unsigned int     destIP; 
}; 

//Header TCP 
struct tcphdr 
{ 
   unsigned short sport; 
   unsigned short dport; 
   unsigned int   seqnum; 
   unsigned int   acknum; 
   unsigned char  DataOffset; 
   unsigned char  Flags; 
   unsigned short Windows; 
   unsigned short Checksum; 
   unsigned short UrgPointer; 
}; 

// main entry 
int main(int argc, char *argv[]) 
{ 
    // private 
    WSADATA             wsa;     
    int                 s; 
    unsigned int        on=1; 
    struct iphdr        *ip; 
    struct tcphdr       *tcp; 
    struct sockaddr_in  to; 
    struct in_addr      addr; 
    char                buffer[1024]; 

    // setup winsock 
    WSAStartup(MAKEWORD(2,2), &wsa); 

    // create socket 
    if((s = socket(AF_INET, SOCK_RAW, IPPROTO_TCP))==-1){ 
        printf("socket() error\n"); 
        return 0; 
    } 

    // set some options 
    if (setsockopt(s, IPPROTO_IP, IP_HDRINCL, (char*)&on, sizeof(on)) == -1){ 
        printf("setsockopt() error\n"); 
        return -1; 
    } 

    // create header 
    ip = (struct iphdr*) buffer; 
    tcp = (struct tcphdr*) (buffer + sizeof(struct iphdr)); 

    memset(ip, 0, sizeof(struct iphdr)); 
    ip->ver      = 4; 
    ip->len      = 5; 
    ip->total_len    = htons(sizeof(struct iphdr) + sizeof(struct tcphdr)); 
    ip->ident        = 2; 
    ip->ttl          = 255; 
    ip->proto        = IPPROTO_TCP; 
    ip->sourceIP = inet_addr("192.168.1.11"); 
    ip->destIP       = inet_addr("192.168.1.12"); 

    memset(tcp, 0, sizeof(struct tcphdr)); 
    tcp->sport = htons(1024); 
    tcp->dport = htons(54321); 
    tcp->seqnum  = 2; 
    tcp->DataOffset  = 5; 
    tcp->acknum  = 1; 
    tcp->Windows = htons(65535); 

    to.sin_addr.S_un.S_addr  = ip->destIP; 
    to.sin_family = AF_INET; 
    to.sin_port = tcp->dport; 

    printf("Ziel: %s:%i\n", inet_ntoa(to.sin_addr), ntohs(tcp->dport )); 
    addr.s_addr = ip->sourceIP ; 
    printf("Quelle: %s:%i\n", inet_ntoa(addr), ntohs(tcp->sport )); 

    if(sendto(s, buffer, ntohs(ip->total_len ), 0, (struct sockaddr*)&to, sizeof(to))==-1){ 
        perror("sendto() error"); 
    } 

    // quit 
    getchar(); 
    return 0; 
}

// create socket 
    if((s = socket(AF_INET, SOCK_RAW, IPPROTO_RAW))==-1){ 
        printf("socket() error\n"); 
        return 0; 
    }