计算机网络ping实验报告

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6、r line distance for a, to b vertical box distance for b, list can measured课 程 设 计 课程名称计算机网络课程设计题目名称_ PING程序设计_学生学院_自动化学院_ 专业班级_ _ 学 号 学生姓名_ _ 指导教师_ _ 200 9 年 12 月 30 日摘要本说明书主要包括了ping程序设计的设计目的、ping程序的工作原理以及设计方案，重点介绍了ping程序的源代码，并且附带了实验结果以及总结等。关键字：ping 程序设计目 录 TOC o 1-6 h z u HYPERLINK l _Toc250055090

7、1 实验设计目的及要求 PAGEREF _Toc250055090 h 3 HYPERLINK l _Toc250055091 1.1设计目的 PAGEREF _Toc250055091 h 3 HYPERLINK l _Toc250055092 1.2设计要求 PAGEREF _Toc250055092 h 3 HYPERLINK l _Toc250055093 2实验内容 PAGEREF _Toc250055093 h 3 HYPERLINK l _Toc250055094 2.1定义数据结构 PAGEREF _Toc250055094 h 3 HYPERLINK l _Toc250055

8、095 2.2程序实现 PAGEREF _Toc250055095 h 3 HYPERLINK l _Toc250055096 2.3程序要求 PAGEREF _Toc250055096 h 3 HYPERLINK l _Toc250055097 3ping工作原理及设计方案 PAGEREF _Toc250055097 h 3 HYPERLINK l _Toc250055098 3.1设计思路 PAGEREF _Toc250055098 h 3 HYPERLINK l _Toc250055100 3.2设计方案 PAGEREF _Toc250055100 h 4 HYPERLINK l _To

9、c250055102 3.3ping源程序 PAGEREF _Toc250055102 h 4 HYPERLINK l _Toc250055310 4实验结果 PAGEREF _Toc250055310 h 7 HYPERLINK l _Toc250055311 5总结 PAGEREF _Toc250055311 h 7 HYPERLINK l _Toc250055313 6参考文献 PAGEREF _Toc250055313 h 71 实验设计目的及要求设计目的PING程序是我们使用的比较多的用于测试网络连通性的程序。PING程序基于ICMP，使用ICMP的回送请求和回送应答来工作。由计算机

10、网络课程知道，ICMP是基于IP的一个协议，ICMP包通过IP的封装之后传递。课程设计中选取PING程序的设计，其目的是希望同学们通过PING程序的设计，能初步掌握TCP/IP网络协议的基本实现方法，对网络的实现机制有进一步的认识。设计要求RAW模式的SOCKET编程PING程序是面向用户的应用程序，该程序使用ICMP的封装机制，通过IP协议来工作。为了实现直接对IP和ICMP包进行操作，实验中使用RAW模式的SOCKET编程。熟悉SOCKET的编程，包括基本的系统调用如SOCKET、BIND等；实验内容定义数据结构需要定义好IP数据报、ICMP包等相关的数据结构；程序实现在WINDOWS环境

11、下实现PING程序；程序要求在命令提示符下输入： PING .其中为目的主机的IP地址，不要求支持域名，对是否带有开关变量也不做要求。不带开关变量时，要求返回4次响应。返回信息的格式： REPLY FROM .或 REQUEST TimeOut （无法PING通的情况）。ping工作原理及设计方案设计思路由于Ping是基于ICMP协议，因此需要使用windows socket中的RAW模式进行编程，首先定义好IP数据包头，接着在IP数据包头的基础上定义ICMP数据包头，由于需要计算回送时间，因此还需要ICMP回送数据的结构。Ping的具体实现流程可以分为以下几点：首先创建SOCKET，然后根据

12、主机名查询地址；接着调用PING主程序对目标主机地址进行测试，测试过程包含相关信息的处理；最后显示回复，并关闭SOCKET设计方案IP头与ICMP头的设置分别参照RFC791及RFC792的标准，包含所有必要信息。主程序设置main（）函数，用于数据包发送及接收，其中，数据包发送调用另一函数void send_packet()，数据包接收调用void recv_packet( )，由于发送数据包时可能会遇到阻塞或者目标主机不通，造成超时，因此需要在发送数据包后调用一个函数判断是否超时，此处设置函数setsockopt（）来实现超时判断；其次，还需要一个函数来计算CRC校验和，此处设置为sign

13、ed short cal_chksum( )，校验和采用移位方法进行计算。ping源程序/ ping.cpp : 定义控制台应用程序的入口点。#include#include#include#define SEND_SIZE 32 #define PACKET_SIZE 4096#define ICMP_ECHO 8#define ICMP_ECHOREPLY 0#pragma comment(lib,Ws2_32.lib)struct icmpunsigned char icmp_type; /类型unsigned char icmp_code; /编码unsigned short icmp

14、_chksum; /校验和unsigned short icmp_id; /标示符unsigned short icmp_seq; /顺序号unsigned long icmp_data; /数据;struct ipunsigned char ip_hl:4; /报头长度unsigned char ip_v:4; /版本号unsigned char ip_tos; /服务类型unsigned short ip_len; /总长度unsigned short ip_id; /标识unsigned short ip_off; /标志unsigned char ip_ttl; /生存时间unsign

15、ed char ip_p; /协议号unsigned short ip_sum; /报头校验和unsigned long ip_src; /源IP地址unsigned long ip_dst; /目的IP地址;char sendpacketPACKET_SIZE;char recvpacketPACKET_SIZE;struct sockaddr_in dest_addr; struct sockaddr_in from_addr;int sockfd;int pid;unsigned short cal_chksum(unsigned short *addr,int len);int pac

16、k(int pack_no);int unpack(unsigned char *buf,int len);void send_packet(void);void recv_packet(void);int main(int argc, CHAR* argv)struct hostent *host;struct protoent *protocol;int timeout=1000;int SEND_COUNT=4;int i;char *par_host;char m_Input100;printf(Input IP: );gets(m_Input);par_host=m_Input;WO

17、RD wVersionRequested;WSADATA wsaData;int err;wVersionRequested = MAKEWORD( 2, 2 );err = WSAStartup( wVersionRequested, &wsaData );if ( err != 0 ) return;if ( LOBYTE( wsaData.wVersion ) != 2 |HIBYTE( wsaData.wVersion ) != 2 ) WSACleanup( );return; if( (protocol=getprotobyname(icmp) )=NULL) /返回对应于给定协议

18、名的包含名字和协议号 printf(getprotobyname errorn); /的protoent结构指针exit(1);if( (sockfd=socket(AF_INET,SOCK_RAW,protocol-p_proto) )0) printf(socket errorn);exit(1); if(setsockopt(sockfd,SOL_SOCKET,SO_RCVTIMEO,(char*)&timeout,sizeof(timeout)0) /设置套接口的选项fprintf(stderr,failed to set recv timeout: %dn,WSAGetLastErr

19、or();if(setsockopt(sockfd,SOL_SOCKET,SO_SNDTIMEO,(char*)&timeout,sizeof(timeout)h_addr,host-h_length);/resolve address to hostnameif(host=gethostbyaddr(host-h_addr,4,PF_INET) par_host=host-h_name; else if( dest_addr.sin_addr.s_addr=inet_addr(par_host)=INADDR_NONE)printf(Unkown host %sn,par_host);exi

20、t(1);pid=_getpid();printf(Pinging %s %s: with %d bytes of data:nn,par_host,inet_ntoa(dest_addr.sin_addr),SEND_SIZE); for(i=0;i1) sum+=*w+;nleft-=2;if( nleft=1) /处理ICMP报头为奇数个字节时累加最后一个 *(unsigned char *)(&answer)=*(unsigned char *)w;sum+=answer;sum=(sum16)+(sum&0 xffff);sum+=(sum16);answer=sum;return

21、answer;/打包int pack(int pack_no) int packsize;struct icmp *icmp;packsize=8+SEND_SIZE;icmp=(struct icmp*)sendpacket;icmp-icmp_type=ICMP_ECHO;icmp-icmp_code=0;icmp-icmp_chksum=0;icmp-icmp_seq=pack_no;icmp-icmp_id=pid;icmp-icmp_data=GetTickCount(); icmp-icmp_chksum=cal_chksum( (unsigned short *)icmp,pac

22、ksize); /*校验算法*/return packsize;/解包int unpack(char *buf,int len) struct ip *ip;struct icmp *icmp;double rtt;int iphdrlen;ip=(struct ip *)buf;iphdrlen=ip-ip_hl*4; icmp=(struct icmp *)(buf+iphdrlen); if( (icmp-icmp_type=ICMP_ECHOREPLY) & (icmp-icmp_id=pid) ) len=len-iphdrlen-8; rtt=GetTickCount()-icmp-icmp_data; printf(R