Linux网络编程系列:
如果对Linux网络编程,对socket通信不是太清楚的同学,强烈推荐看一下上述的预备知识,说不定,就会喜欢上Linux的网络编程世界
本系列会尽量对协议的部分进行介绍, 结合简单应用例子进行掌握学习.
ping程序功能实现
效果展示
在这里插入图片描述
ping.c程序代码
/*
* @Author: D-lyw
* @Date: 2018-11-01 17:00:20
* @Last Modified by: D-lyw
* @Last Modified time: 2018-12-01 17:01:42
* @Description 在Linux环境利用socket编程,基于ICMP协议实现ping功能
*/
#include "ping.h"
#include <stdio.h>
#include <string.h>
#include <netdb.h> // struct icpmhdr, struct iphdr , gethostbyname, hostent
#include <arpa/inet.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <netinet/ip_icmp.h>
#include <sys/time.h>
char sendbuf[1024]; // 用来存放将要发送的ip数据包
struct sockaddr_in sockaddr, recvsock;
int sockaddr_len = sizeof(struct sockaddr);
struct hostent *host;
int sockfd;
int ping_time = 5;
int main(int argc, char const *argv[])
{
if(argc != 2){
fprintf(stderr, "Usage: ping <remote_hostname>\n", argv[0]);
exit(1);
}
int on = 1;
int pid;
int psend = 0, precv = 0;
memset(&sockaddr, 0, sizeof(struct sockaddr));
if((sockaddr.sin_addr.s_addr = inet_addr(argv[1])) == INADDR_NONE){
// 说明输入的主机名不是点分十进制,采用域名方式解析
if((host = gethostbyname(argv[1])) == NULL){
fprintf(stderr, "ping %s , 未知的名称!\n", argv[1]);
exit(1);
}
sockaddr.sin_addr = *(struct in_addr *)(host->h_addr);
}
sockaddr.sin_family = AF_INET;
// 创建原始套接字 SOCK_RAW 协议类型 IPPROTO_ICMP
if((sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP)) == -1){
fprintf(stderr, "%s\n", strerror(errno));
}
setuid(getpid());
pid = getpid();
// 发包操作
printf("PINGing %s %d data send.\n", argv[1], ICMP_DATA_LEN);
int i = 1;
int recvDataLen;
int sendDatalen;
char *recvbuf[1024];
while(ping_time--){
int packlen = packping(i++);
if((sendDatalen = sendto(sockfd, sendbuf, packlen,0, (struct sockaddr *)&sockaddr, sizeof(sockaddr))) < 0){
fprintf(stderr, "send ping package %d error, %s\n", i, strerror(errno));
continue ;
}
if((recvDataLen = recvfrom(sockfd, recvbuf, sizeof(recvbuf), 0, (struct sockaddr *)&recvsock, &sockaddr_len)) == -1){
fprintf(stderr, "recvmsg error, %s\n", strerror(errno));
continue;
}
decodepack(recvbuf, recvDataLen);
sleep(1);
}
return 0;
}
// 发送ping数据包
int packping(int sendsqe){
struct icmp *icmp_hdr; // icmp头部指针
icmp_hdr = (struct icmp *)sendbuf;
icmp_hdr->icmp_type = ICMP_ECHO;
icmp_hdr->icmp_code = 0;
icmp_hdr->icmp_hun.ih_idseq.icd_id = getpid();
icmp_hdr->icmp_hun.ih_idseq.icd_seq = sendsqe;
memset(icmp_hdr->icmp_data, 0, ICMP_DATA_LEN);
gettimeofday((struct timeval *)icmp_hdr->icmp_data, NULL);
int icmp_total_len = 8 + ICMP_DATA_LEN;
icmp_hdr->icmp_cksum = 0;
icmp_hdr->icmp_cksum = checksum((unsigned char *)(sendbuf),icmp_total_len);
return icmp_total_len;
}
int decodepack(char *buf, int len){
struct iphdr *ip_hdr;
struct icmp *icmp_hdr;
int iph_lenthg;
float rtt; // 往返时间
struct timeval end; // 接收报文时的时间戳
ip_hdr = (struct iphdr *)buf;
// ip头部长度
iph_lenthg = ip_hdr->ihl<<2;
icmp_hdr = (struct icmp *)(buf + iph_lenthg);
// icmp报文的长度
len -= iph_lenthg;
if(len < 8){
fprintf(stderr, "Icmp package length less 8 bytes , error!\n");
return -1;
}
// 确认是本机发出的icmp报文的响应
if(icmp_hdr->icmp_type != ICMP_ECHOREPLY || icmp_hdr->icmp_hun.ih_idseq.icd_id != getpid()){
fprintf(stderr, "Don't send to us!");
return -1;
}
gettimeofday(&end, NULL);
rtt = timesubtract((struct timeval *)&icmp_hdr->icmp_data, &end);
printf("Received %d bytes from %s, ttl = %d, rtt = %f ms, icmpseq = %d \n", len, inet_ntoa(recvsock.sin_addr),ip_hdr->ttl, rtt, icmp_hdr->icmp_seq);
return 0;
}
// 计算时间差
float timesubtract(struct timeval *begin, struct timeval *end){
int n;// 先计算两个时间点相差多少微秒
n = ( end->tv_sec - begin->tv_sec ) * 1000000
+ ( end->tv_usec - begin->tv_usec );
// 转化为毫秒返回
return (float) (n / 1000);
}
// 校验和生成
ushort checksum(unsigned char *buf, int len){
unsigned int sum=0;
unsigned short *cbuf;
cbuf=(unsigned short *)buf;
while(len>1){
sum+=*cbuf++;
len-=2;
}
if(len)
sum+=*(unsigned char *)cbuf;
sum=(sum>>16)+(sum & 0xffff);
sum+=(sum>>16);
return ~sum;
}
ping.h程序代码
#include <netinet/ip_icmp.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <unistd.h>
#include <error.h>
#define IPVERSION 4
#define ICMP_DATA_LEN 56
int packping(int sendsqe);
ushort checksum(unsigned char *buf, int len);
int decodepack(char *buf, int len);
float timesubtract(struct timeval *begin, struct timeval *end);
