杭州电子科技大学实验报告学生姓名：韩民杨学号：12081420 指导教师：吴端坡实验地点：1#108 实验时间：2015-4-24一、实验室名称：1#108二、实验项目名称：计算机网络实验1Coding on error dectecting algorithms(C++)三、实验学时：四、实验原理：C++编程五、实验目的：利用C++编程CRC16校验及奇偶校验六、实验内容：Coding on error dectecting algorithms(C++)1.Cyclic redundancy checkUsing the polynomials below to encode random generated data stream (40-100bits). Show the FEC, and encoded data frame.CRC-4 x4+x+1 ITU G.704CRC-16 x16+x15+x2+1 IBM SDLCCRC-32 x32+x26+x23+ (x2)x+1ZIP, RAR, IEEE 802 LAN/FDDI, IEEE1394, PPP-FCSFor the error patter listed below, what the conclusion does the receiver get? Can the receiver find the errors?Case Error patternNo error 0000 (0000)One error 1000 (000)Two errors 100 (001)Random errors Random error pattern2.Parity checkUsing even or odd parity check on random generated data stream (8-20bits).Show encoded data frame.For the error patter listed below, what the conclusion does the receiver get? Can the receiver find the errors?Case Error patternNo error 0000 (0000)One error 1000 (000)Two errors 100 (001)七、实验器材（设备、元器件）：PC机一台，装有C++集成开发环境。

八、实验步骤：#include<stdio.h>#include<stdlib.h>#include<memory.h>#include<string.h>#include<conio.h>#include<time.h>#define NO_ERROR 1#define ONE_ERROR 2#define TWO_ERROR 3#define RANDOM_ERROR 4#define RESULT 1#define CRC 0#define Parity 0#define check 1int flag_parity;//判断奇偶校验void ByteToBit(char* out,const char* in,int bits);void input_message(char*message);int xor(char **p, char *d,int len);char *crc_function(char *str_p,int len,char *dividend,int len_d,int type,char *crc_p ); char Parity_check(char *message_output,int length,int mode);void main(){ int pattern = 0;int channel_way =0;char message[8]={NULL};// data that produced by chancechar message_output[1000] = {NULL};char message_crc[] = {NULL};//transportint length; //message's length/*这是固定了为4为的crc，当这里改变是就可以直接改变crc的长度了*/ char dividend[]="10011";char message_input[1000]="";/*这里可以更改数值当时16为crc的时候，此时的len_d为15*/int len_d=5;//被除数长度设置char flag;while (true){ fflush(stdin);//任意输入数据printf("please input the message!\n");gets(message);printf("A need to send this message:%s\n",message);length = strlen(message);ByteToBit(message_output,message,length*8);for(int k = 0;k<length*8;k++){ printf("%d",message_output[k]);message_input[k] = message_output[k]+48;}pattern = 0;channel_way =0;printf("\n");printf("Coding on error dectecting algorithms\n");printf(" 1.Cyclic redundancy check\n");printf(" 2.Parity check \n");printf(" please chice pattern: \n");/*选择进入的检错模式*/scanf("%d",&pattern);fflush(stdin);//清空缓存区if(pattern == 1).{printf("*************************************\n");printf(" analog channel\n");printf(" please choice the way of error\n");printf("**** 1.No error *****\n");printf("**** 2.One error *****\n");printf("**** 3.Two errors *****\n");printf("**** 4.Random errors *****\n");scanf("%d",&channel_way);printf("\ncrc：");//进行crc检测int len = length*8;//printf("%d\n",len);char *crc = NULL;crc = crc_function(message_input,len,dividend,len_d,CRC,NULL);for(int i = 0;i < len_d;i++){printf("%c",*crc);message_input[length*8+i] = *crc;crc+=1;}printf("\n");/*模拟信道Case Error patternNo error 0000 (0000)One error 1000 (000)Two errors 100 (001)Random errors Random error pattern*/if(channel_way == NO_ERROR){char *result = NULL;int flagg=0;printf("信道中传输数据：");for(int f =0;f<length*8+len_d-1 ;f++)printf("%c",message_input[f]);printf("\n");printf("正在检错中.......\n");printf("检错结果：");fflush(stdin);result = crc_function(message_input,len,dividend,len_d,RESULT,crc-len_d);for(int i = 0;i < len_d-1;i++){printf("%c",*result);.if((*result) - 48 != 0){printf("\n error! \n");flagg =1;break;}result+=1;}if(flagg == 0)printf("\n no error! \n");}if(channel_way == ONE_ERROR){char *result = NULL;message_input[0] = ((message_input[0] - 48)^('1'-48)) + 48;printf("信道中传输数据：");for(int f =0;f<length*8+len_d-1 ;f++)printf("%c",message_input[f]);printf("\n");printf("正在检错中.......");printf("检错结果：");result = crc_function(message_input,len,dividend,len_d,RESULT,crc-len_d);for(int i = 0;i < len_d-1;i++){if(*result == '1'){printf("data error! \n");break;}else{continue;result+=1;}}}if(channel_way == TWO_ERROR){char *result = NULL;message_input[0] = ((message_input[0] - 48)^('1'-48)) + 48;message_input[length*8-1] = ((message_input[length*8-1] - 48)^('1'-48)) + 48;printf("信道中传输数据：");.for(int f =0;f<length*8+len_d-1 ;f++)printf("%c",message_input[f]);printf("\n");printf("正在检错中.......");printf("检错结果：");result = crc_function(message_input,len,dividend,len_d,RESULT,crc);for(int i = 0;i < len_d-1;i++){if(*result != '0'){ printf(" data error! \n");break;}else{ continue;result+=1;}}}if(channel_way == RANDOM_ERROR){char *result = NULL;int no;srand( (unsigned)time( NULL ) ); //初始化随机数no = rand()%length*8;message_input[no] = ((message_input[0] - 48)^('1'-48)) + 48;printf("信道中传输数据：");for(int f =0;f<length*8+len_d-1 ;f++)printf("%c",message_input[f]);printf("\n");printf("正在检错中.......\n");printf("检错结果：");result = crc_function(message_input,len,dividend,len_d,RESULT,crc);for(int i = 0;i < len_d-1;i++){if(*result != '0'){printf(" data error! \n");break;}else{continue;.result+=1;}}}printf("************************************\n");printf("\n");printf("\n");}else{printf("Please select the parity mode\n");printf(" 1.Even parity \n");printf(" 2.Odd parity\n");scanf("%d",&flag_parity);char m = Parity_check(message_input,length*8,Parity);printf("在信道中传输的message:");message_input[length*8] = m ;for(int message_number = 0;message_number<=length*8;message_number++)printf("%c",message_input[message_number]);printf("\n");printf("*************************************\n");printf("****** analog channel ******\n");printf("***please choice the way of error****\n");printf("**** 1.No error *****\n");printf("**** 2.One error *****\n");printf("**** 3.Two errors *****\n");scanf("%d",&channel_way);if(channel_way == NO_ERROR){for(int f =0;f<length*8;f++)printf("%c",message_input[f]);printf("正在检错中.......\n");printf("检错结果：");char flag_parity_mode = Parity_check(message_input,length*8,check);if(flag_parity_mode == (message_input[length*8]))printf("no error!\n");}if(channel_way == ONE_ERROR){message_input[0] = ((message_input[0] - 48)^('1'-48)) + 48;for(int f =0;f<length*8;f++)printf("%c",message_input[f]);.printf("正在检错中.......\n");printf("检错结果：");char flag_parity_mode = Parity_check(message_input,length*8,check);printf(" error!\n");}if(channel_way == TWO_ERROR){message_input[0] = ((message_input[0] - 48)^('1'-48)) + 48;message_input[length*8-1] = ((message_input[length*8-1] - 48)^('1'-48)) + 48;for(int f =0;f<length*8;f++)printf("%c",message_input[f]);printf("正在检错中.......\n");printf("检错结果：");char flag_parity_mode = Parity_check(message_input,length*8,check);printf("no error!\n");}printf("************************************\n");printf("\n");printf("\n");}fflush(stdin);printf("do you want to continue？y/n\n");scanf("%c",&flag);if(flag == 'y')continue;elsebreak;}}/***********************************************/function：完成字节转换成位的功能/输入字符：In 输出的二进制：Out************************************************/void ByteToBit(char* out,const char* in,int bits){//char out_1[1000] = "";int i;// printf("%s\n",in);for(i=0;i<bits;++i){out[bits-i-1]=(in[i>>3]>>(i&7))&1;// printf("%d:%d\n",i,out[i]);}}/***********************************************/function：完成异或除法/输入：**p *d/输出：直接将一次异或除法之后的结果覆盖************************************************/int xor(char **p, char *d,int len=5){//p为message,d 为crc检测的中的pint i=0;for(;i<len;i++){**p=(**p-48)^(*d-48)+48;*p=*p+1;d=d+1;}d=d-len; //d重新指向最新的//*p=*p-len+1;//p后移一位return 0;}/***********************************************/function：完成crc检错以及crc计算/输入：传输字符：str_p 传输字符长度len/ 4位的crc的检错方式len_d是需要填0的个数/ type 用于判断显示计算传输之后的结果还是计算crc/输出：crc或者计算传输之后的结果************************************************/char *crc_function(char *str_p,int len,char *dividend,int len_d,int type,char *crc_p=NULL){int i;int j;char *input_p=(char *)malloc(sizeof(char)*(len+len_d-1)); //申请空间char *input_p_tmp=NULL;input_p_tmp=input_p;//向指针指向的内存里存数据for(i=0;i<len;i++){*input_p_tmp=str_p[i];input_p_tmp++;}/*补零个数为len_d-1*/for(i=0;i<len_d-1;i++){if(type==CRC){//如果是求crc就补0*input_p_tmp='0';input_p_tmp++;}else{//如果是求结果就补crc*input_p_tmp=*crc_p;crc_p++;input_p_tmp++;}}input_p_tmp=NULL;//开始检查如果是1则进行异或除法,如果是0就指针向下移动一位.其中'0'=48for(j=0;j<len;j++){/*把1传入48表示为"0";*/if(*input_p==48){//指针后移一位input_p=input_p+1;}else{xor(&input_p,dividend,len_d);}}return input_p;}/***********************************************/function：完成奇偶校验/输入：message_output为需要传输的数据以及数据的长度lengh 奇偶校验的模式/输出：返回奇偶校验的结果************************************************/ char Parity_check(char *message_output,int length,int mode) {fflush(stdin);int j = 0;//偶校验if(flag_parity== 1){ if(mode == Parity){ for(int i = 0;i<length;i++){ if(message_output[i] == 49)j++;elsecontinue;}if(j%2 == 0)return '0';elsereturn '1';}else{ for(int i = 0;i<length;i++){if(message_output[i] == 49)j++;elsecontinue;}if(j%2 == 0)return '0';elsereturn '1';}}//奇校验else if(flag_parity == 0){if(mode == Parity){for(int i = 0;i<length;i++){if(message_output[i] == 49)j++;elsecontinue;}if(j%2 == 1)return '0';elsereturn '1';}else{for(int i = 0;i<length;i++){if(message_output[i] == 49)j++;elsecontinue;}if(j%2 == 1)return '0';elsereturn '1';}}}九、实验数据及结果分析：1.输入界面2.输入数据3.CRC校验1）No error2）One error3）Two errors4）Random errors4.奇偶校验①界面②Even parity 1）No error2）One error③Odd parity1)No error3)Two errors十、实验结论：奇偶校验，1位错可发现，2位错不可发现（奇数个错可发现，偶数个错不可发现）。