CBN协议实现(c语言).doc

中文注释编程实现一个GBN传输协议的发送方和接收方两程序，采用编程语言不限，要求能将发送接收流程以及处理方法表现出来.附源代码及注释源代码：三：GBN-CS.c#include GBN.h#include #include #include extern int TRACE ; /* 用于跟踪 */ extern int nsim ; /* 当前第5层到第4层的信息数 */ extern int nsimmax; /*msg生成数量,直到停止，生成的最大信息数 */extern float time; /时间extern int packet_correct; /包的正确到达数extern int packet_resent; /包的重传数extern struct event *evlist; /事件int main() /主函数struct event *eventptr;/变量，结构体声明struct msg msg2give;struct pkt pkt2give;int i,j;char c; init();/初始化 A_init();/A端初始化 B_init();/B端初始化 while (1) /循环，用于每个包的传送 eventptr = evlist; /* 从模拟器得到下一个事件 */ if (eventptr=NULL)goto terminate; evlist = evlist-next;/* 从事件清单改变该事件 */ if (evlist!=NULL)evlist-prev=NULL;if (TRACE = 2)/打印与事件相关的信息printf(n事件时间: %f,eventptr-evtime);printf( 类型: %d,eventptr-evtype);if (eventptr-evtype=0)printf(, 计时器中断： );else if (eventptr-evtype=1)printf(, 来自第五层 );elseprintf(, 来自第三层 );if (eventptr-eventity = A)/打印事件实体printf( 通信实体: %d A端n,eventptr-eventity); elseprintf( 通信实体: %d B端n,eventptr-eventity); time = eventptr-evtime; /* 更新下一个事件的时间 */if (nsim=nsimmax)break; /* 当输入包个数等于生成的最大包个数，模拟器停止 */ if (eventptr-evtype = FROM_LAYER5 ) /如果事件调用来自第五层generate_next_arrival(); /* 为将来的包的到达做准备 */ /* 将相同的信息转换为字母字符串 */ j = nsim % 26; for (i=0; i2)printf( 学生发送的主要数据是: );for (i=0; ieventity = A)/A端向外发送数据A_output(msg2give); else/B端向外发送数据B_output(msg2give); else if (eventptr-evtype = FROM_LAYER3)/如果事件调用来自第三层pkt2give.seqnum = eventptr-pktptr-seqnum; pkt2give.acknum = eventptr-pktptr-acknum; pkt2give.checksum = eventptr-pktptr-checksum; for (i=0; ipktptr-payloadi;if (eventptr-eventity = A) /* A端交付包*/ A_input(pkt2give); /* 适当的实体*/else /* B端交付包*/B_input(pkt2give);free(eventptr-pktptr); /* 释放包的缓存 */else if (eventptr-evtype = TIMER_INTERRUPT)/计时器中断情况if (eventptr-eventity = A) A_timerinterrupt();elseB_timerinterrupt();else /校检,防止发生不可预料事件printf(内部警告: 不可预知的事件类型！ n); free(eventptr); terminate:/终止 printf( 模拟器停止在： %f s n ，从第五层发送了 %d个包n,time,nsim); printf( 正确发送包的个数: %d n, packet_correct); printf( 重发包的个数: %d n, packet_resent); system(pause);/暂停一GBN.h#pragma once#include /基础功能模块的数据结构声明#define BIDIRECTIONAL 1 /* 改变值1如果你需要写额外的可靠程序或B输出程序(即B端系统)*/* msg结构体是由第五层（教师代码）转变成第四层的数据单元（学生代码）*/*它包括了经由第五层向学生层协议通信实体交付的数据（字符）*/struct msg char data20;/* pkt结构体是第4层（学生代码）向第3层传送的数据单元（老师代码）。值得注意的是预先定义的包结构,这一切学生必须遵守。*/struct pktint seqnum;/顺序号int acknum;/应答号int checksum;/检查和char payload20;#define WINDOWSIZE 8 /定义滑动窗口大小#define MAXBUFSIZE 50/最大窗口大小#define RTT 15.0/周游时间#define NOTUSED 0/没用到#define NACK -1/否定应答#define TRUE 1#define FALSE 0#define A 0#define B 1/网络仿真部分数据结构声明*struct eventfloat evtime; /* 事件时间 */int evtype; /* 事件类型 */int eventity; /* 事件实体*/struct pkt *pktptr; /* 指向这个事件的指针（如果需要） */struct event *prev; /前一事件struct event *next; /后一事件 ;/* possible events: */#define TIMER_INTERRUPT 0 /事件中断#define FROM_LAYER5 1 /来自第五层#define FROM_LAYER3 2 /来自第三层#define OFF 0#define ON 1/基础功能模块的函数声明*void ComputeChecksum(struct pkt *packet);/计算校验和int CheckCorrupted(struct pkt packet);/检查数据是否出错void A_output( struct msg message);/A端向外发送数据void A_input(struct pkt packet);/A端接收数据void A_timerinterrupt();/A计时器超时void A_init();/A端初始化void B_output(struct msg message); void B_input(struct pkt packet);void B_timerinterrupt();void B_init();/网络仿真部分的函数声明*void init(); /初始化仿真器float jimsrand();/随机数发生器0,1/处理事件列表部分的函数声明*void generate_next_arrival();/产生下一个到达的分组void insertevent(struct event *p);/向事件列表中插入一条新的事件void printevlist();/打印事件列表/*/*计时器模块*void stoptimer(int);/停止计时器void starttimer(int,float);/启动计时器/*/*网络各层之间传送模块*void tolayer3(int AorB,struct pkt packet);/向第3层发送信息void tolayer5(int AorB,char datasent20);/向第5层发送信息二：#include GBN.h#include #include #include extern int TRACE = 1; /* 用于跟踪*/extern int nsim = 0; /* 当前第5层到第4层的信息数*/ extern int nsimmax = 0; /* msg生成数量,直到停止*/extern float time = 0.000;float lossprob; /* 丢包可能性*/float corruptprob; /* 包的数据位数丢失可能性*/float lambda; /* 从第五层到达的比率 */ int ntolayer3; /* 送往第3层的包数量*/static int nlost = 0; /* 在媒体中丢失的包数量*/static int ncorrupt = 0; /* 在网络中被破坏的包*/static int expectedseqnum = 0; /* 期待接收方发送的序号 */static int nextseqnum; /* 下一次发送方要使用的包序号*/static int base; /* 发送方头窗*/struct pkt winbufWINDOWSIZE; /* 窗口包缓冲区*/static int winfront,winrear; /* 缓冲区的头尾指针*/static int pktnum;/* 缓冲窗口包的数量*/struct msg bufferMAXBUFSIZE; /* 发送方数据缓冲区*/int buffront,bufrear; /* 缓冲区的头尾指针 */static int msgnum;/* 缓冲窗口包的数量 */关于各种包的类型定义/*int packet_lost =0; /包丢失int packet_corrupt=0; /包破坏int packet_sent =0; /包发送extern int packet_correct=0;/正确包extern int packet_resent =0;/重发包int packet_timeout=0;/超时包extern struct event *evlist = NULL; /* 事件清单 */相关接口函数的实现/计算校验和,即脚链和1的补码和void ComputeChecksum( struct pkt *packet) int checksum;int i;checksum = packet-seqnum;checksum = checksum + packet-acknum;/求脚链for ( i=0; ipayloadi);checksum = 0-checksum;/取反packet-checksum = checksum;/检查是否出错int CheckCorrupted(struct pkt packet)int checksum;int i;checksum = packet.seqnum;checksum = checksum + packet.acknum;for ( i=0; i20; i+ ) checksum = checksum + (int)(packet.payloadi);if ( (packet.checksum+checksum) = 0 )/检查校检和是否相加为0return (FALSE);elsereturn (TRUE);/A端向外发送数据/* 被第五层调用，向另一端发送数据*/void A_output(struct msg message)int i;struct pkt sendpkt;/* 如果的发送方下次使用序号小于滑动窗口的最大序号，那么补发包*/if ( nextseqnum base+WINDOWSIZE )printf(-A：新的包到达，发送窗口不满，新的包送往第3层！n);/* 创建包 */sendpkt.seqnum = nextseqnum;sendpkt.acknum = NOTUSED;for ( i=0; i20 ; i+ ) sendpkt.payloadi = message.datai;/* 检查是否出错 */ComputeChecksum (&sendpkt); /* 送出包 */ tolayer3 (A, sendpkt); /* 复制这些包到窗口缓冲区 */ winrear = (winrear+1)%WINDOWSIZE; pktnum +; winbufwinrear = sendpkt; for (i=0; i20; i+) winbufwinrear.payloadi= sendpkt.payloadi; /* 更新状态变量 */ nextseqnum = nextseqnum+1; starttimer(A,RTT); B_input(sendpkt); A_input(sendpkt);/* 如果移动窗口包满*/else printf(-A:新的包到达，发送窗口已满!);/* 如果缓冲区满，放弃并退出*/if ( msgnum = MAXBUFSIZE)printf ( 错误：发送缓冲区已满 ！n); exit (1); /* 否则，将信息送入缓冲区 */ else printf(信息已送入缓冲区n); bufrear = (bufrear+1) % MAXBUFSIZE; /拥塞控制,防止拥塞,减小缓冲区 for (i=0; i20; i+) bufferbufrear.datai = message.datai; msgnum +; /B端向外发送数据/* 被第五层调用，发送数据到另一方,同A方相似 */void B_output(struct msg message)int i;struct pkt sendpkt;/* 如果发送窗口不满*/if ( nextseqnum base+WINDOWSIZE )printf(-B：新的包到达，发送窗口不满，新的包送往第3层！!n);/* create packet */sendpkt.seqnum = nextseqnum;sendpkt.acknum = NOTUSED;for ( i=0; i20 ; i+ ) sendpkt.payloadi = message.datai;/* computer checksum */ComputeChecksum (&sendpkt); /* send out packet */ tolayer3 (A, sendpkt);A_input(sendpkt); /* copy the packet to window packet buffer */ winrear = (winrear+1)%WINDOWSIZE; pktnum +; winbufwinrear = sendpkt; for (i=0; i20; i+) winbufwinrear.payloadi= sendpkt.payloadi; /* if it is the first packet in window, start timeout */ /if ( base = nextseqnum ) / /starttimer(A,RTT); /printf(-A: start a new timer!n); / /* update state variables */ nextseqnum = nextseqnum+1;/* 如果发送窗口满*/else printf(-B:新的包到达，发送窗口已满!,);/* if buffer full, give up and exit*/if ( msgnum = MAXBUFSIZE)printf ( 错误：发送缓冲区已满 ！ n); exit (1); /* otherwise, buffer the message */ else printf(缓冲区满!n); bufrear = (bufrear+1) % MAXBUFSIZE; for (i=0; i20; i+) bufferbufrear.datai = message.datai; msgnum +; /A端接收数据void A_input(struct pkt packet)struct pkt sendpkt;int i;/* 如果收到没有被破坏的包并且确认包收到*/ if ( (CheckCorrupted(packet) = FALSE) & (packet.acknum != NACK) )printf(-A: ACK(确认包) %d 被正确的收到,packet.acknum);packet_correct+; /* 从窗口缓冲区删去被确认的包*/ winfront = (winfront+(packet.acknum+1-base) % WINDOWSIZE; pktnum = pktnum - (packet.acknum+1-base); /* 改变窗口最小号确认包 */ base = packet.acknum+1; stoptimer(A); if ( base nextseqnum) /starttimer(A,RTT); printf (nnn发送新的包!); /* 如果缓冲区不空发送新的包*/ while ( (msgnum!=0) & (nextseqnumbase+WINDOWSIZE) )/* 创建包*/ sendpkt.seqnum = nextseqnum; sendpkt.acknum = NOTUSED; buffront = (buffront+1) % MAXBUFSIZE; for ( i=0; i20 ; i+ ) sendpkt.payloadi = bufferbuffront.datai; /* 和确认*/ ComputeChecksum (&sendpkt); /*如果是滑动窗口的第一个包，开始超时检测*/ if ( base = nextseqnum ) /如果滑动窗口最小的包等于下一次要发送的序号/starttimer(A,RTT);printf (发送新的包!n); /* 送出包 */ tolayer3 (A, sendpkt); /* 复制包到窗口缓冲区 */ winrear = (winrear+1)%WINDOWSIZE; winbufwinrear = sendpkt; pktnum +; /* 更新状态变量 */nextseqnum = nextseqnum+1; /* 删除缓冲区的包 */msgnum -;else printf (-A: 收到否定应答，什么也没有完成!n);/B端接收数据*一定要调用这个/* 这只是单一的A到B的传送方式，没有B端的数据发出 */* 被第三层调用，但数据到达B端第4层*/void B_input(struct pkt packet) struct pkt sendpkt;int i;/*如果收到没有被破坏的包并且确认包收到 */if ( (CheckCorrupted(packet) = FALSE) & (packet.seqnum = expectedseqnum)printf(n-B: 包正确的到达，发送ACK确认包n,packet.seqnum);/* 发送应答包 */ /* create packet */ sendpkt.seqnum = NOTUSED; sendpkt.acknum = expectedseqnum; for ( i=0; i20 ; i+ )sendpkt.payloadi = 0; /* computer checksum */ ComputeChecksum (&sendpkt); /* send out packet */tolayer3 (B, sendpkt);/* update state variables */expectedseqnum = expectedseqnum+1; printf(-B:expectedseqnum (期待下一次的发送序号)= %dn,expectedseqnum); /* 发送包到第五层 */ /tolayer5(B,packet.payload); /* 否则，抛弃包，发送否定应答*/ elseprintf(-B: 包 %d 损坏或者不是我所需要的, 发送否定应答!n,packet.seqnum); /* 创建包 */ sendpkt.seqnum = NOTUSED; sendpkt.acknum = NACK; for ( i=0; i20 ; i+ ) sendpkt.payloadi = 0; /* 校检和检查 */ ComputeChecksum (&sendpkt); /* 发出包 */ tolayer3 (B, sendpkt); /A计时器超时/* A超时被调用 */void A_timerinterrupt()int i;printf(-A:超时！重新发包!n);/* start timer */starttimer(A,RTT);/* 重新发送所有未被确认的包*/for ( i=1; i=pktnum; i+ )packet_resent+; tolayer3(A,winbuf(winfront+i)%WINDOWSIZE); /B计时器超时/* called when Bs timer goes off */void B_timerinterrupt()int i;printf(-B: 超时！重新发包!n);/* start timer */starttimer(B,RTT);/* 重新发送所有未被确认的包 */for ( i=1; i 0.0: ); /fscanf(fp,%f,&lambda);scanf(%f,&lambda); printf(n输入跟踪: );/fscanf(fp,%d,&TRACE);scanf(%d,&TRACE);printf(nn);srand(9999); /* init random number generator */sum = 0.0; /* test random number generator for students */for (i=0; i1000; i+)sum=sum+jimsrand(); /* jimsrand() should be uniform in 0,1 */avg = sum/1000.0; /*if(avg 0.75) printf(It is likely that random number generation on your machinen ); printf(is different from what this emulator expects. Please taken); printf(a look at the routine jimsrand() in the emulator code. Sorry. n); exit(0); */ printf(%f,avg);ntolayer3 = 0;nlost = 0;ncorrupt = 0;time=0.0; /* initialize time to 0.0 */ generate_next_arrival(); /* initialize event list */随机数发生器float jimsrand() double mmm = 2147483647; /* largest int - MACHINE DEPENDENT! */float x; /* individual students may need to change mmm */ x = rand()/mmm; /* x should be uniform in 0,1 */return(x); /*/*事件处理部分*void generate_next_arrival()double x,log(),ceil();struct event *evptr;float ttime;int tempint;/if (TRACE2)/printf(-GENERATE NEXT ARRIVAL: creating new arrivaln);x = lambda*jimsrand()*2; /* x is uniform on 0,2*lambda */ /* having mean of lambda */evptr = (struct event *)malloc(sizeof(struct event);evptr-evtime = time + x; evptr-evtype = FROM_LAYER5;if (jimsrand()eventity = A;elseevptr-eventity = B;insertevent(evptr);/向事件列表中插入一条新的事件void insertevent(struct event *p) struct event *q,*qold;if (TRACE2)/printf( INSERTEVENT: time is %lfn,time);/printf( INSERTEVENT: future time will be %lfn,p-evtime); q = evlist; /* q points to front of list in which p struct inserted q指针指向表前部当p结构被插入*/if (q=NULL)/* 表是空的*/ evlist=p; p-next=NULL; p-prev=NULL; else for (qold = q; q !=NULL & p-evtime q-evtime; q=q-next)qold=q; if (q=NULL)/* 表尾 */ qold-next = p; p-prev = qold; p-next = NULL;else if (q=evlist)/* front of list */ p-next=evlist; p-prev=NULL; p-next-prev=p; evlist = p;else /* 表中部 */ p-next=q; p-prev=q-prev; q-prev-next=p; q-prev=p;/打印事件列表void printevlist()struct event *q;int i;printf(-n事件列表如下:n);for(q = evlist; q!=NULL; q=q-next)printf(事件时间: %f, 类型: %d 实体: %dn,q-evtime,q-evtype,q-eventity); printf(-n);/启动计时器void starttimer(int AorB,float increment)struct event *q;struct event *evptr;if (TRACE2)printf(n-A: 启动计时器: 在 %f 开始定时n,time);/* 友好的：检查计时器是否早已开始计时，如果是，则发出警告*/*