实现类似ping功能的C源代码

早些年学习网络协议的时候折腾而写的代码，代码在后面。

纯粹代码的意义不大，建议有兴趣学习的童鞋，要想学习ping，最好能了解一下 RFC 792 ICMP协议，这个比代码纯粹的代码有意义，当年咱学习的时候，可没人给这样的建议啊，这可是本人后来逐渐明白的，什么才是最重要的，在此点出来，明白的有缘人自然能明白。

直接将以下代码存为文件xping.cpp或xping.c，用VC直接编译就可以（VC自己会提示生成工程），GCC编译也可以的

//
//xping
//awzzz
//2002/06/20
//
#include 
#include 
#include 
#include 
#ifdef WIN32
#define WIN32_LEAN_AND_MEAN
#include 
#pragma comment(lib, "Wsock32.lib")
#else
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#endif
#define ICMP_ECHO 8 
#define ICMP_ECHOREPLY 0
//#define ICMP_MIN 8 // minimum 8 byte icmp packet (just header) 
#define ICMP_MIN (8 + 4) // minimum 8 byte icmp packet (just header + timestamp)
// IP header
typedef struct _tagX_iphdr
{
unsigned char h_len:4;           // length of the header 
unsigned char version:4;         // Version of IP 
unsigned char tos;              // Type of service 
unsigned short total_len;       // total length of the packet
unsigned short ident;           // unique identifier 
unsigned short frag_and_flags; // flags 

unsigned char ttl;     // ttl
unsigned char proto;            // protocol (TCP, UDP etc) 
unsigned short checksum;        // IP checksum 

unsigned int sourceIP; 
unsigned int destIP; 
}XIpHeader;
// ICMP header
typedef struct _tagX_icmphdr
{
unsigned char i_type;
unsigned char i_code;
unsigned short i_cksum;
unsigned short i_id;
unsigned short i_seq;
unsigned long i_timestamp;
}XIcmpHeader;
//puclic code
//网际校验和生产算法
//网际校验和是被校验数据16位值的反码和(ones-complement sum)
unsigned short in_cksum(unsigned short* addr, int len)
{
int   nleft = len;
int   sum = 0;
unsigned short* w = addr;
unsigned short answer = 0;

while(nleft > 1) {
   sum += *w++;
   nleft -= 2;
}
if(nleft == 1) {
   *(unsigned char*)(&answer) = *(unsigned char*)w;
   sum += answer;
}
sum = (sum >> 16) + (sum & 0xffff);
sum += (sum >> 16);
answer = ~sum;
return (answer);
}
void fill_IpHeader(char *buf)
{
// XIpHeader *ip_hdr = (XIpHeader *)buf;
}
void fill_IcmpData(char *buf, int datasize)
{
if (buf)
{
   char ch = 0;
   char* icmpdata = buf + sizeof(XIcmpHeader);
   fprintf(stdout, "(IcmpData)\r\n");
   for (int i = 0; i < datasize; i++)
   {
    ch = 'A' + i%('z' - 'A');
    *(icmpdata + i) = ch;
    fprintf(stdout, "%c", ch);
   }
   fprintf(stdout, "\r\n");
}
}
void fill_IcmpHeader(char *buf, int datasize)
{
static unsigned short seq_no = 0;
XIcmpHeader *icmp_hdr = (XIcmpHeader *)buf;
if (icmp_hdr)
{
   icmp_hdr->i_type = ICMP_ECHO;
   icmp_hdr->i_code = 0;
   icmp_hdr->i_cksum = 0;
#ifdef WIN32
   icmp_hdr->i_id = (unsigned short)GetCurrentProcessId(); 
#else
   icmp_hdr->i_id = (unsigned short)getpid(); 
#endif
   icmp_hdr->i_seq = seq_no++;
#ifdef WIN32
   icmp_hdr->i_timestamp = (unsigned long)::GetTickCount();
#else
   icmp_hdr->i_timestamp = (unsigned long)time(NULL);
#endif
   icmp_hdr->i_cksum = in_cksum((unsigned short*)buf, sizeof(XIcmpHeader) + datasize);
   fprintf(stdout, "(IcmpHeader)\r\n");
   fprintf(stdout, "%02X%02X%04X\r\n", icmp_hdr->i_type, icmp_hdr->i_code, icmp_hdr->i_cksum);
   fprintf(stdout, "%04X%04X\r\n", icmp_hdr->i_id, icmp_hdr->i_seq);
   fprintf(stdout, "%08X\r\n", icmp_hdr->i_timestamp);
}
}
// decode
void decode_IpIcmp(char *buf, int size)
{
XIpHeader *ip_hdr = (XIpHeader *)buf;
unsigned short iphdrlen;
if (ip_hdr)
{
   fprintf(stdout, "(IpHeader)\r\n");
   fprintf(stdout, "%01X%01X%02X%04X\r\n", ip_hdr->version, ip_hdr->h_len, ip_hdr->tos, ip_hdr->total_len);
   fprintf(stdout, "%04X%04X\r\n", ip_hdr->ident, ip_hdr->frag_and_flags);
   fprintf(stdout, "%02X%02X%04X\r\n", ip_hdr->ttl, ip_hdr->proto, ip_hdr->checksum);
   //iphdrlen = ip_hdr->h_len * 4; // number of 32-bit words *4 = bytes
   iphdrlen = ip_hdr->h_len << 2; // number of 32-bit words *4 = bytes
   fprintf(stdout, "(IcmpHeader)\r\n");
   if (size < iphdrlen + ICMP_MIN)
   {
    fprintf(stdout, "Reply %d bytes Too few\r\n", size);
   }
   else
   {
    XIcmpHeader *icmp_hdr = (XIcmpHeader *)(buf + iphdrlen);
    fprintf(stdout, "%02X%02X%04X\r\n", icmp_hdr->i_type, icmp_hdr->i_code, icmp_hdr->i_cksum);
    fprintf(stdout, "%04X%04X\r\n", icmp_hdr->i_id, icmp_hdr->i_seq);
    fprintf(stdout, "%08X\r\n", icmp_hdr->i_timestamp);
/*   
    fprintf(stdout, "(IcmpData)\r\n");
    int iIcmpDataSize = size - iphdrlen - sizeof(XIcmpHeader);
    char *icmpdata = buf + iIcmpDataSize;
    for (int i = 0; i < iIcmpDataSize; i++)
     fprintf(stdout, "%c", *(icmpdata + i));
    fprintf(stdout, "\r\n");
*/
    unsigned long timestamp = 0;
#ifdef WIN32
    timestamp = (unsigned long)::GetTickCount();
#else
    timestamp = (unsigned long)time(NULL);;
#endif
    timestamp -= icmp_hdr->i_timestamp;
    struct sockaddr_in from;
    from.sin_addr.s_addr = ip_hdr->sourceIP;
    fprintf(stdout, "Reply %d bytes from: %s time<%d TTL=%d icmp_seq=%d\r\n",
     size,
     inet_ntoa(from.sin_addr),
     timestamp,
     ip_hdr->ttl,
     icmp_hdr->i_seq
     );
   }
}
}
int main(int argc, char **argv)
{
int ret = 0;
#ifdef WIN32
WSADATA ws;
WSAStartup(0x0101,&ws);
//#else
// ;
#endif
int iIcmpDataSize = 0;
struct sockaddr_in dest,from;
unsigned int addr = 0;
struct hostent *hp;

char buffer[1024];
char recv_buffer[1024];
if(argc < 2)
{
   fprintf(stderr, "Usage: %s [host|ip] [datasize]\r\n", argv[0]);
   return 0;
}
if (argc > 2)
   iIcmpDataSize = atoi(argv[2]);
if (iIcmpDataSize < 1 || iIcmpDataSize > 1024)
   iIcmpDataSize = 10;
memset(&dest, 0, sizeof dest);
dest.sin_family = AF_INET;
hp = gethostbyname(argv[1]);
if (!hp)
   addr = inet_addr(argv[1]);
if ((!hp) && (addr == INADDR_NONE))
{
   fprintf(stderr,"Unable to resolve %s\r\n",argv[1]);
   return 0;
}
if (hp != NULL)
   memcpy(&(dest.sin_addr), hp->h_addr,hp->h_length);
else
   dest.sin_addr.s_addr = addr;
#ifdef WIN32
// ;
#else
setuid(getuid());
// setuid(0);
#endif
int sockfd;
sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
fprintf(stdout, "XPing...\r\n");
for (int i = 0; i < 3; i++)
{
   fprintf(stdout, "Echo...\r\n");
   memset(buffer, 0, 1024);
   fill_IcmpData(buffer, iIcmpDataSize);
   fill_IcmpHeader(buffer, iIcmpDataSize);
   XIcmpHeader *icmp_hdr = (XIcmpHeader *)buffer;
   int iSendSize = sendto(sockfd, buffer, sizeof(XIcmpHeader) + iIcmpDataSize, 0, (struct sockaddr*)&dest, sizeof(dest));
   fprintf(stdout, "Reply...\r\n");
   memset(&from, 0, sizeof from);
   memset(recv_buffer, 0, 1024);
#ifdef WIN32
   int fromlen = sizeof(from);
   int iRecvSize = recvfrom(sockfd, recv_buffer, 1024, 0, (struct sockaddr*)&from,   &fromlen);
#else
   socklen_t fromlen = sizeof(from);
   int iRecvSize = recvfrom(sockfd, recv_buffer, 1024, 0, (struct sockaddr*)&from,   &fromlen);
#endif
   if (iRecvSize > 0)
    decode_IpIcmp(recv_buffer, iRecvSize);
}
#ifdef WIN32
WSACleanup();
//#else
// ;
#endif
return ret;
}

早些年网络不发达（现在依然很落后），没有博客？幸好这个代码当时也还是扔到网上了，最近发现，在这里博客一下，算是复习记载。