滑动窗口协议设计报告滑动窗口协议设计1、引言随着网络的不断壮大，用户数量、信息量的需求不断增加，网络负荷越来越重。
此时，我们迫切需要一种机制来控制网络的流量，减少网络拥堵的几率，提高传输的效率。
因此，一种名为滑动窗口的协议应运而生。
滑动窗口协议，是TCP使用的一种流量控制方法。
该协议允许发送方在停止并等待确认前可以连续发送多个分组。
由于发送方不必每发一个分组就停下来等待确认，因此该协议可以加速数据的传输。
经测试证明，该协议还能有效地解决TCP的高协议处理开销和UDP的低可靠性之间的矛盾。
2、实验目的基本原理2.1 窗口机制滑动窗口协议的基本原理就是在任意时刻，发送方都维持了一个连续的允许发送的帧的序号，称为发送窗口；同时，接收方也维持了一个连续的允许接收的帧的序号，称为接收窗口。
发送窗口和接收窗口的序号的上下界不一定要一样，甚至大小也可以不同。
不同的滑动窗口协议窗口大小一般不同。
发送方窗口内的序号代表了那些已经被发送，但是还没有被确认的帧，或者是那些可以被发送的帧。
接受方为其窗口内的每一个序号保留了一个缓冲区。
与每个缓冲区相关联的还有一位，用来指明该缓冲区是满的还是空的。
3、实验原理TCP滑动窗口用来暂存两台计算机问要传送的数据分组。
每台运行TCP协议的计算机有两个滑动窗口：一个用于数据发送，另一个用于数据接收。
发送端待发数据分组在缓冲区排队等待送出。
被滑动窗口框入的分组，是可以在未收到接收确认的情况下最多送出的部分。
滑动窗口左端标志X的分组，是已经被接收端确认收到的分组。
随着新的确认到来，窗口不断向右滑动4、实验代码#include<stdio.h>#include <stdlib.h>#include <windows.h>//加这个头文件#include <windowsx.h>#include <iostream>#include <winsock.h>#include<conio.h>#include<time.h>#include <math.h>#define NULL 0#define MAX_LENGTH 2000#define RECEIVE_MAX_LENGTH 1500#define SEND_MAX_LENGTH 1500#define TIMEOUT 1#define WSA_WAIT_TIMEOUT -1#define MAXPOOL 100#define SLEEPMS 1000#define SOCKET_DISCONN 0#pragma comment(lib,"ws2_32.lib")#pragma warning(disable:4996)typedef enum { data = 1, ack, nak, tout } frame_kind; //帧类型CRITICAL_SECTION gCS;int socketClient;int ret;typedef struct frame_head{frame_kind kind; //帧类型unsigned int seq; //序列号unsigned int ack; //确认号unsigned char data[MAX_LENGTH]; //数据}Head;typedef struct frame{frame_head head; //帧头unsigned int size; //数据的大小} Frame;typedef struct framenode //队列节点类型{frame head_data;struct framenode *next;} Framenode;typedef struct{Framenode *front; //队头指针Framenode *rear; //队尾指针} LinkQueue;void InitLine(LinkQueue *q){q->front = q->rear =NULL;}int QueueEmpty(LinkQueue *q){return q->front == NULL && q->rear == NULL; }frame QueueFront(LinkQueue *q){if (QueueEmpty(q)){printf("队列为空！\n");Sleep(SLEEPMS);exit(0);}return q->front->head_data;}int QueueLen(LinkQueue *q){if (QueueEmpty(q)){return 0;}int num = 0;Framenode *p = q->front;while (p != NULL){num++;p = p->next;}return num;}void GetFrameFromHost(LinkQueue *q){if (QueueLen(q) >= MAXPOOL){printf("data %d 已准备好\n", q->front->head_data.head.seq);return;}Framenode *p = (Framenode *)malloc(sizeof(Framenode));memset(p->head_data.head.data, 0, MAX_LENGTH);srand((unsigned)time(NULL));p->head_data.size = rand() % MAX_LENGTH; // 帧大小随机生成memset(p->head_data.head.data, '1', p->head_data.size);p->head_data.head.ack = -1;p->head_data.head.kind = data;p->head_data.head.seq = 0;p->next = NULL;if (QueueEmpty(q))q->front = q->rear = p; // 首帧是待发送的帧else{p->head_data.head.seq = (q->rear->head_data.head.seq + 1) % MAXPOOL;q->rear->next = p;q->rear = p;}printf("从主机得到：data %d，放入缓存\n", p->head_data.head.seq);GetFrameFromHost(q); // 由于实验需要，假设主机有足够多的数据帧要发送}void DeLine(LinkQueue *q){Framenode *p = NULL;if (QueueEmpty(q)){printf("队列为空！\n");}else{p = q->front;q->front = p->next;if (q->rear == p) q->rear = NULL;printf("发送data %d, %d 成功！从缓存中删除\n", p->head_data.head.seq, p->head_data.size);free(p);p = NULL;}}void main(){printf("建立连接 ... \n");Begin:WORD wVersionRequested;DWORD WINAPI ReceiveFun(LPVOID pParam);WSADATA wsaData; //初始化socket库wVersionRequested = MAKEWORD(1, 1); //两个byte型合并成一个WORD型int err = WSAStartup(wVersionRequested, &wsaData);if (err != 0){Sleep(SLEEPMS);return;}if (LOBYTE(wsaData.wVersion) != 1 || HIBYTE(wsaData.wVersion) != 1){WSACleanup(); //中止Windows Sockets服务 WSAStartup()成对使用Sleep(SLEEPMS);return;}socketClient = socket(AF_INET, SOCK_STREAM, 0);//监听的套接字SOCKADDR_IN clientadd;clientadd.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");clientadd.sin_family = AF_INET;clientadd.sin_port = htons(7001);//设置连接端的IP、端口if (SOCKET_ERROR ==connect(socketClient, (SOCKADDR*)&clientadd, sizeof(SOCKADDR))) //连接{WSACleanup();Sleep(SLEEPMS);goto Begin;}char getData[RECEIVE_MAX_LENGTH];memset(getData, 0, RECEIVE_MAX_LENGTH); //清零if (recv(socketClient, getData, RECEIVE_MAX_LENGTH, 0) == SOCKET_ERROR) //接受printf("接受连接提示信息出错！\n");}else{printf("%s\n", getData);}char sendData[SEND_MAX_LENGTH];memset(sendData, 0, SEND_MAX_LENGTH);strcpy(sendData, "你好接收方，我是发送方！");if (SOCKET_ERROR == send(socketClient, sendData, strlen(sendData) + 1, 0)) //发送{printf("发送连接提示信息出错！\n");WSACleanup();closesocket(socketClient);Sleep(SLEEPMS);return;}printf("按任意键继续！\n");while (!kbhit()) {}; //等待开始Sleep(SLEEPMS);printf("1bit滑动窗口协议：发送方，发送窗口=1\n");LinkQueue QueueQ;InitLine(&QueueQ);frame packetsend; //dataframe packetreceive; // ack,nakunsigned long tick = GetTickCount();int ret = 0;HANDLE hThread;while (1){GetFrameFromHost(&QueueQ); //从主机取数据帧memset(&packetsend, 0, sizeof(packetsend));Sleep(SLEEPMS);printf("\n");packetsend = QueueFront(&QueueQ); //取数据帧ret = send(socketClient, (char *)&packetsend, sizeof(packetsend), 0);//发送dataif (ret == SOCKET_ERROR){printf("发送数据出错！\n");continue;}printf("发送数据帧：data %d, %d\n", packetsend.head.seq, packetsend.size);const unsigned long timeOut = 5 * 1000; //设置超时计时器 5秒超时memset(&packetreceive, 0, sizeof(packetreceive));Sleep(SLEEPMS);printf("\n");InitializeCriticalSection(&gCS); // 初始化临界区hThread = CreateThread(NULL, 0, ReceiveFun, (LPVOID)&packetreceive, 0, NULL);int r = WaitForMultipleObjects(1, &hThread, TRUE, timeOut);DeleteCriticalSection(&gCS); //与InitializeCriticalSection(&gCS);成对使用if (ret == SOCKET_ERROR || ret == SOCKET_DISCONN){printf("接受出错！Press any key to continue\n");while (!kbhit()) {};continue;}if (r == WSA_WAIT_TIMEOUT) //判断超时{TerminateThread(hThread, 0); //终止线程printf("超时重传：data %d, %d\n", packetsend.head.seq, packetsend.size);}else if (packetsend.head.seq == packetreceive.head.ack){srand((unsigned)time(NULL));switch (rand() % 5) //假定产生随机结果，20%的概率超时{case 0:printf("接收方发送回复超时(ack丢失模拟)：%d\n", packetsend.head.seq);printf("超时重传：data %d, %d\n", packetsend.head.seq, packetsend.size);break;default:if (packetreceive.head.kind == ack){printf("接受ack帧：ack %d\n", packetreceive.head.ack);DeLine(&QueueQ);}else if (packetreceive.head.kind == nak){printf("接受nak帧：nak %d\n", packetsend.head.seq);}break;}}else printf("帧序号出错： %d\n", packetreceive.head.ack);if (GetTickCount() - tick > 20 * TIMEOUT) //设置时间20秒{printf("持续时间20s. 按q退出，其他键继续\n");int kbc = getch();if (kbc == 'q' || kbc == 'Q')break;}}printf("按任意键退出！\n");while (!kbhit()) {};Sleep(SLEEPMS);printf("谢谢使用！\n");WSACleanup();closesocket(socketClient);Sleep(SLEEPMS);}DWORD WINAPI ReceiveFun(LPVOID pArg){EnterCriticalSection(&gCS);//进入critical sectionframe *packetreceive = (frame *)pArg;ret = recv(socketClient, (char *)packetreceive, sizeof(*packetreceive), 0);LeaveCriticalSection(&gCS); //线程用毕，离开critical sectionreturn ret;}#include<stdio.h>#include <stdlib.h>#include <windows.h>//加这个头文件#include <windowsx.h>#include <iostream>#include <winsock.h>#include<conio.h>#include<time.h>#include <math.h>#define NULL 0#define MAX_LENGTH 2000#define RECEIVE_MAX_LENGTH 1500#define SEND_MAX_LENGTH 1500#define TIMEOUT 1#define WSA_WAIT_TIMEOUT -1#define MAXPOOL 100#define SLEEPMS 1000#define SOCKET_DISCONN 0#pragma comment(lib,"ws2_32.lib")#pragma warning(disable:4996)typedef enum { data = 1, ack, nak, tout } frame_kind; //帧类型CRITICAL_SECTION gCS;int socketClient;int ret;typedef struct frame_head{frame_kind kind; //帧类型unsigned int seq; //序列号unsigned int ack; //确认号unsigned char data[MAX_LENGTH]; //数据}Head;typedef struct frame{frame_head head; //帧头unsigned int size; //数据的大小} Frame;typedef struct framenode //队列节点类型{frame head_data;struct framenode *next;} Framenode;typedef struct{Framenode *front; //队头指针Framenode *rear; //队尾指针} LinkQueue;void InitLine(LinkQueue *q){q->front = q->rear = NULL;}int QueueEmpty(LinkQueue *q){return q->front == NULL && q->rear == NULL; }frame QueueFront(LinkQueue *q){if (QueueEmpty(q)){printf("队列为空！\n");Sleep(SLEEPMS);exit(0);}return q->front->head_data;}int QueueLen(LinkQueue *q){if (QueueEmpty(q)){return 0;}int num = 0;Framenode *p = q->front;while (p != NULL){num++;p = p->next;}return num;}int GetFrameFromHost(LinkQueue *q){if (QueueLen(q) >= MAXPOOL){printf("准备接受：data %d \n", q->front->head_data.head.seq);return q->front->head_data.head.seq;}Framenode *p = (Framenode *)malloc(sizeof(Framenode));memset(p->head_data.head.data, 0, MAX_LENGTH);p->head_data.head.ack = -1;p->head_data.head.seq = 0;p->next = NULL;if (QueueEmpty(q))q->front = q->rear = p;else{p->head_data.head.seq = (q->rear->head_data.head.seq + 1) % MAXPOOL;q->rear->next = p;q->rear = p;}return GetFrameFromHost(q);}int DeLine(LinkQueue *q, frame *pf, unsigned int curw) //假设数据帧送往主机是足够快的{Framenode *p = NULL;if (curw == q->front->head_data.head.seq)p = q->front;elsep = q->rear;if (p->head_data.head.ack != -1) //假定数据已经提交主机{printf("向主机交付data %d, %d 成功！\n", p->head_data.head.ack, p->head_data.size);}memset(p->head_data.head.data, 0, MAX_LENGTH);memcpy(p->head_data.head.data, pf->head.data, pf->size);p->head_data.size = pf->size;p->head_data.head.ack = pf->head.seq; //保存发送帧序号}frame QueueAnswer(LinkQueue *q, unsigned int curw){if (curw == q->front->head_data.head.seq){return q->front->head_data;}else{return q->rear->head_data;}}void main(){Begin:WORD wVersionRequested;WSADATA wsaData; //初始化socket库wVersionRequested = MAKEWORD(1, 1); //两个byte型合并成一个WORD型int err = WSAStartup(wVersionRequested, &wsaData);//使用sockets之前要调用一次if (err != 0){Sleep(SLEEPMS);return;}if (LOBYTE(wsaData.wVersion) != 1 || HIBYTE(wsaData.wVersion) != 1){WSACleanup();//中止Windows Sockets服务 WSAStartup()成对使用Sleep(SLEEPMS);}SOCKET socksrv = socket(AF_INET, SOCK_STREAM, 0);//监听的套接字SOCKADDR_IN socketadd;socketadd.sin_addr.S_un.S_addr = htonl(INADDR_ANY); //监听连接socketadd.sin_family = AF_INET;socketadd.sin_port = htons(7001); //设置端口if (SOCKET_ERROR == bind(socksrv, (SOCKADDR*)&socketadd, sizeof(SOCKADDR))) {printf("绑定出错！\n");WSACleanup();Sleep(SLEEPMS);return;}if (SOCKET_ERROR == listen(socksrv, 5)){printf("监听出错！");WSACleanup();Sleep(SLEEPMS);return;}SOCKADDR_IN sockclient;int len = sizeof(SOCKADDR);SOCKET sockconn = accept(socksrv, (SOCKADDR*)&sockclient, &len);//建立连接的套节字if (INVALID_SOCKET == sockconn){printf("建立连接出错！\n");WSACleanup();Sleep(SLEEPMS);}char sendData[SEND_MAX_LENGTH];memset(sendData, 0, SEND_MAX_LENGTH);sprintf(sendData, "%s", "你好发送方，我是接受方！");if (SOCKET_ERROR == send(sockconn, sendData, strlen(sendData) + 1, 0)){printf("发送连接提示信息出错！\n");WSACleanup();closesocket(sockconn);Sleep(SLEEPMS);return;}char getData[RECEIVE_MAX_LENGTH];memset(getData, 0, RECEIVE_MAX_LENGTH);recv(sockconn, getData, RECEIVE_MAX_LENGTH, 0);printf("%s\n", getData);printf("1bit滑动窗口协议：接收方，接收窗口=1\n");LinkQueue QueueQ;InitLine(&QueueQ);frame packetreceive; //dataframe packetsend; // ack,nakint curw = GetFrameFromHost(&QueueQ);//初始化接收窗口int ret = 0;while (1){memset(&packetreceive, 0, sizeof(packetreceive));Sleep(SLEEPMS);printf("\n");ret = recv(sockconn, (char *)&packetreceive, sizeof(packetreceive), 0);if (ret == SOCKET_ERROR || ret == SOCKET_DISCONN){if (ret == SOCKET_ERROR){printf("连接出错！自动连接！\n");continue;}else{printf("连接已断开，按q退出，其他键等待新的连接\n");int kbc = getch();if (kbc == 'q' || kbc == 'Q')break;else{WSACleanup();closesocket(sockconn);Sleep(SLEEPMS);goto Begin;}}}srand((unsigned)time(NULL));switch (rand() % 5) //假定产生随机结果，20%的概率校验错误或接收发送方超时{case 0:printf("接受数据帧：data %d, %d，校验错误，丢弃(数据帧出错模拟)\n", packetreceive.head.seq, packetreceive.size);memset(&packetsend, 0, sizeof(packetsend));memcpy(&packetsend, &packetreceive, sizeof(packetreceive));packetsend.head.ack = packetreceive.head.seq;packetsend.head.seq = curw;packetsend.head.kind = nak;printf("发送否认帧：nak %d\n", packetreceive.head.seq);break;case 1:packetsend.head.kind = tout;printf("发送方发送数据超时(数据帧丢失模拟)：%d\n", packetreceive.head.seq);break;default:printf("接受数据帧：data %d, %d，校验正确\n", packetreceive.head.seq, packetreceive.size);if (packetreceive.head.seq == (QueueAnswer(&QueueQ, curw)).head.ack){printf("上一帧的重发，丢弃，直接发送确认帧：ack %d\n", packetreceive.head.seq);}else{printf("新的数据帧：data %d, %d，放入缓存\n", packetreceive.head.seq, packetreceive.size);curw = DeLine(&QueueQ, &packetreceive, curw); //将新帧保存待送往主机memset(&packetsend, 0, sizeof(packetsend));packetsend = QueueAnswer(&QueueQ, curw); //待发送的确认帧printf("发送确认帧：ack %d\n", packetreceive.head.seq);}packetsend.head.kind = ack;break;}if (packetsend.head.kind == tout) continue; //发送方使用多线程判断超时ret = send(sockconn, (char *)&packetsend, sizeof(packetsend), 0);if (ret == SOCKET_ERROR){printf("发送ack或nak出错！自动连接！\n");continue;}}printf("按任意键退出！\n");while (!kbhit()) {};Sleep(SLEEPMS);cprintf("谢谢使用！\n");WSACleanup();closesocket(sockconn);Sleep(SLEEPMS);}5、实验截图6、实验分析该滑动窗口协议模拟程序还有进一步完善的余地，例如可以对以下一些地方进行改进：（1）改模拟程序通过命令行来实行，缺少形象直观的界面，希望日后可以设计比较简单明了的界面来展示程序的主要模拟功能。
