简单的服务器、客户端程序实验报告

实验(No. 4)题目:简单的客户/服务器程序设计与实现

实验目的及要求:

1、熟悉Microsoft Visual Studio 2008编程环境。

2、了解TCP与UDP协议,以及它们之间的区别。

3、了解客户/服务器模型原理。

    4、熟悉Socket编程原理,掌握简单的套接字编程。

实验设备:

硬件:PC机(两台以上)、网卡、已经设定好的以太网环境

软件:Microsoft Visual Studio 2008

实验内容及步骤:

1、编写用TCP协议实现的Client端和Server端程序并调试通过。

程序分两部分:客户程序和服务器程序。

工作过程是: 服务器首先启动,它创建套接字之后等待客户的连接;客户启动后创建套接字,然后和服务器建立连接;建立连接后,客户接收键盘输入,然后将数据发送到服务器,服务器收到到数据后,将接收到的字符在屏幕上显示出来。或者服务器接收键盘输入,然后将数据发送到客户机,客户机收到数据后,将接收到的字符在屏幕上显示出来。

程序流程如下:

 


2、编写用UDP协议实现的Client端和Server端程序并调试通过(做完第一个实验的基础上做该实验)。

 

3、编写用TCP协议实现Client端与Server端的一段对话程序。Server端根据用户的输入来提示Client端下一步将要进行操作。

所用函数及结构体参考:

1、创建套接字——socket()

功能:使用前创建一个新的套接字

格式:SOCKET PASCAL FAR socket(int af,  int type,  int procotol);

参数:af:代表网络地址族,目前只有一种取值是有效的,即AF_INET,代表internet地址族;

Type:代表网络协议类型,SOCK_DGRAM代表UDP协议,SOCK_STREAM代表TCP协议;

Protocol:指定网络地址族的特殊协议,目前无用,赋值0即可。

返回值为SOCKET,若返回INVALID_SOCKET则失败。

2、指定本地地址——bind()

功能:将套接字地址与所创建的套接字号联系起来。

格式:int PASCAL FAR bind(SOCKET s,  const struct sockaddr FAR * name,  int namelen);

参数:s: 是由socket()调用返回的并且未作连接的套接字描述符(套接字号)。

其它:没有错误,bind()返回0,否则SOCKET_ERROR

地址结构说明:

struct sockaddr_in

{

short sin_family;//AF_INET

u_short sin_port;//16位端口号,网络字节顺序

struct in_addr sin_addr;//32位IP地址,网络字节顺序

char sin_zero[8];//保留

}

3、建立套接字连接——connect()和accept()

功能:共同完成连接工作

格式:int PASCAL FAR connect(SOCKET s,  const struct sockaddr FAR * name,  int namelen);

SOCKET PASCAL FAR accept(SOCKET s,  struct sockaddr FAR * name,  int FAR * addrlen);

参数:s: 是由socket()调用返回的并且未作连接的套接字描述符(套接字号)。

4、监听连接——listen()

功能:用于面向连接服务器,表明它愿意接收连接。

格式:int PASCAL FAR listen(SOCKET s,  int backlog);

5、数据传输——send()与recv()

功能:数据的发送与接收

格式:int PASCAL FAR send(SOCKET s,  const char FAR* buf,  int len,  int flags);

int PASCAL FAR recv(SOCKET s,  const char FAR * buf,  int len,  int flags);

参数:buf:指向存有传输数据的缓冲区的指针。

6、多路复用——select()

功能:用来检测一个或多个套接字状态。

格式:int PASCAL FAR select(int nfds,  fd_set FAR* readfds,  fd_set FAR* writefds,

fd_set FAR * exceptfds,  const struct timeval FAR* timeout);

参数:readfds:指向要做读检测的指针

writefds:指向要做写检测的指针

exceptfds:指向要检测是否出错的指针

timeout:最大等待时间

7、关闭套接字——closesocket()

功能:关闭套接字s

格式:BOOL PASCAL FAR closesocket (SOCKET s);

8、WSADATA类型和LPWSADATA类型

WSADATA类型是一个结构,描述了Socket库的一些相关信息,其结构定义如下:

typedef struct WSAData {

        WORD                    wVersion;

        WORD                    wHighVersion;

        char                    szDescription[WSADESCRIPTION_LEN+1];

        char                    szSystemStatus[WSASYS_STATUS_LEN+1];

        unsigned short          iMaxSockets;

        unsigned short          iMaxUdpDg;

        char FAR *              lpVendorInfo;

} WSADATA;

typedef WSADATA FAR *LPWSADATA;

值得注意的就是wVersion字段,存储了Socket的版本类型。LPWSADATA是WSADATA的指针类型。它们不用程序员手动填写,而是通过Socket的初始化函数WSAStartup读取出来。

9、sockaddr_in、in_addr类型

sockaddr_in定义了socket发送和接收数据包的地址。

定义:

struct sockaddr_in {

        short   sin_family;

        u_short sin_port;

        struct  in_addr  sin_addr;

        char    sin_zero[8];

};

其中in_addr的定义如下:

struct in_addr {

        union {

                struct { u_char s_b1,s_b2,s_b3,s_b4; } S_un_b;

                struct { u_short s_w1,s_w2; } S_un_w;

                u_long S_addr;

        } S_un;

首先阐述in_addr的含义,很显然它是一个存储ip地址的联合体,有三种表达方式:

(1)用四个字节来表示IP地址的四个数字;

(2)用两个双字节来表示IP地址;

(3)用一个长整型来表示IP地址。

给in_addr赋值的一种最简单方法是使用inet_addr函数,它可以把一个代表IP地址的字符串赋值转换为in_addr类型,如

addrto.sin_addr.s_addr=inet_addr("192.168.0.2");

本例子中由于是广播地址,所以没有使用这个函数。其反函数是inet_ntoa,可以把一个in_addr类型转换为一个字符串。

sockaddr_in的含义比in_addr的含义要广泛,其各个字段的含义和取值如下:

第一个字段short   sin_family,代表网络地址族,如前所述,只能取值AF_INET;

第二个字段u_short sin_port,代表IP地址端口,由程序员指定;

第三个字段struct in_addr sin_addr,代表IP地址;

第四个字段char    sin_zero[8],是为了保证sockaddr_in与SOCKADDR类型的长度相等而填充进来的字段。

Sever端代码:

// server.cpp : 定义控制台应用程序的入口点。

#include <winsock.h>

#include <windows.h>

#include <stdio.h>

#include <stdlib.h>

#pragma comment(lib, "WS2_32")

SOCKET sock1,sock2;

int sin_size ;

struct sockaddr_in my_addr,their_addr;

char name[20];

//初始化函数Tcp

void Init()

{   

    printf("\n\n\n                                    Server:  TCP\n\n\n");

                                    //建立套接字

                                    const WORD wMinver=0x0101;

                                    WSADATA wsadata;

                                    if(0!=::WSAStartup(wMinver,&wsadata))

                                          perror("Start socket error!");

    if(INVALID_SOCKET==(sock1=::socket(AF_INET,SOCK_STREAM,0)))

                                                 perror("Create socket error!");

                                   

                                    my_addr.sin_family=AF_INET;

                                    my_addr.sin_addr.S_un.S_addr=INADDR_ANY;

                                    my_addr.sin_port=htons(1000);

                                    if(SOCKET_ERROR==::bind(sock1,(struct sockaddr*)&my_addr,sizeof(my_addr)))

                                    {

                                          perror("Binding stream socket");

                                          exit(1);

                                    }

                                    //开始侦听

                                    if(SOCKET_ERROR==::listen(sock1,5))

                                    {

                                          perror("Listening stream socket");

                                          exit(1);

                                    }

                                    //接受连接

                                    printf("                      Ready to serve client. Please connect...\n\n\n");

                                    sin_size = sizeof(struct sockaddr_in);

                                    if((sock2=accept(sock1,(struct sockaddr *)&their_addr,&sin_size))==-1)

                                    {

                                          perror("Accepting stream socket");

                                          exit(1);

                                    }

    printf("                          Accepting a new connet:%s",inet_ntoa(their_addr.sin_addr));

}

//选择菜单

int menu()

{

                                    char *s=(char*)malloc(2*sizeof(char));

                                   

                                    int c;

                                    printf("\n\n\n                                    Server:  Menu\n\n\n");

                                    printf("                          *********************************\n\n");

                                    printf("                          *      1.Send      Message      *\n");

                                    printf("                          *      2.Receive   Message      *\n");

                                    printf("                          *      3.Exit                   *\n\n");

                                    printf("                          *********************************\n");

                                    do

                                    {

                                          printf("\n                           Enter your choice:");

                                          gets(s);

                                          if(s[0]=='\0'){

                                                 gets(s);

                                          }

                                          c=atoi(s);

                                    }while(c<0||c>3);

                                    free(s);

                                    return c;

}

//消息发送函数

void Send()

{

                                    char Msg[10240];

                                    printf("\nPlease Input the message:");

                                    gets(Msg);

    Msg[10239]='\0';

    ::send(sock2,Msg,strlen(Msg),0);

}

//消息接收函数

void Receive()

{

                                    int len;

                                    char buf[10240];

                                    for(int i=0;i<10240;i++){

                                          buf[i]='\0';

                                    }

    if((len=::recv(sock2,buf,10240,0))==-1)

                                    {

                                          perror("Receving data error");

                                          exit(1);

                                    }

                                    printf("The Received Message:%s\n",buf);

                                   

                                   

}

//主函数

void main()

{   

                                    Init();

                                    for(;;)

                                    {

                                          switch(menu())

                                          {

                                          case 1:

                                                 Send();

                                                 break;

                                          case 2:

                                                 Receive();

                                                 break;

                                          case 3:

                                                 exit(0);

                                          }

                                    }

                                    //::closesocket(sock2);

                                    ::closesocket(sock1);

                                    ::WSACleanup();

}

Server端界面:

Client端代码:

// client.cpp : 定义控制台应用程序的入口点。//

#include <winsock.h>

#include <windows.h>

#include <stdio.h>

#include <stdlib.h>

#pragma comment(lib, "WS2_32")

SOCKET sock1,sock2;

int sin_size ;

struct sockaddr_in my_addr,their_addr;

char name[20];

//初始化函数Tcp

void Init()

{   

    printf("\n\n\n                                    Client:  TCP\n\n\n");

                                    //建立套接字

                                    const WORD wMinver=0x0101;

                                    WSADATA wsadata;

                                    if(0!=::WSAStartup(wMinver,&wsadata))

                                          perror("Start socket error!");

    if(INVALID_SOCKET==(sock1=::socket(AF_INET,SOCK_STREAM,0)))

                                                 perror("Create socket error!");

                                   

                                    my_addr.sin_family=AF_INET;

                                    my_addr.sin_addr.S_un.S_addr=inet_addr("192.168.93.48");

                                    my_addr.sin_port=htons(1000);

                                   

                                    //请求连接

                                    printf("                                     connecting...");

                                    sin_size = sizeof(struct sockaddr_in);

                                    if(sock2=(::connect(sock1,(LPSOCKADDR)&my_addr,sin_size))==-1)

                                    {

                                          perror("Accepting stream socket");

                                          exit(1);

                                    }

}

//选择菜单

int menu()

{

                                    char *s=(char*)malloc(2*sizeof(char));

                                   

                                    int c;

                                    printf("\n\n\n                                    Client:  Menu\n\n\n");

                                    printf("                          *********************************\n\n");

                                    printf("                          *      1.Send      Message      *\n");

                                    printf("                          *      2.Receive   Message      *\n");

                                    printf("                          *      3.Exit                   *\n\n");

                                    printf("                          *********************************\n");

                                    do

                                    {

                                          printf("\n                           Enter your choice:");

                                          gets(s);

                                          if(s[0]=='\0'){

                                                 gets(s);

                                          }

                                          c=atoi(s);

                                    }while(c<0||c>3);

                                    free(s);

                                    return c;

}

//消息发送函数

void Send()

{

                                    char Msg[10240];

                                    printf("\nPlease Input the message:");

                                    gets(Msg);

    Msg[10239]='\0';

    ::send(sock1,Msg,strlen(Msg),0);

  

}

//消息接收函数

void Receive()

{

                                    int len;

                                    char buf[10240];

                                    for(int i=0;i<10240;i++){

                                          buf[i]='\0';

                                    }

    if((len=::recv(sock1,buf,10240,0))==-1)

                                    {

                                          perror("Receving data error");

                                          exit(1);

                                    }

                                    printf("The Received Message:%s\n",buf);

                                   

                                   

}

//主函数

void main()

{   

                                    Init();

                                    for(;;)

                                    {

                                          switch(menu())

                                          {

                                          case 1:

                                                 Send();

                                                 break;

                                          case 2:

                                                 Receive();

                                                 break;

                                          case 3:

                                                 exit(0);

                                          }

                                    }

                                    ::closesocket(sock2);

                                    ::closesocket(sock1);

                                    ::WSACleanup();

}

Client端界面:

实验结果及心得:

实验结果截图:

客户端向服务端发送信息:

客户端接收服务端消息:

服务端接收消息:

实验心得:

 通过本次实验及课上老师讲解,了解了TCP与UDP协议和它们之间的区别,以及客户/服务器模型的原理。通过C/S代码的编写运行,形象地看到客户/服务器端的运作方式,对于C/S模型有了很深刻的印象以及进一步理解。通过代码的编写,再一次熟悉Socket编程原理,掌握简单的套接字编程。

第一次运行程序成功后,是在同一台电脑上进行C与S端的连接。在课上实验,将程序放在 2台台式机上进行运行,在与同学探讨中又将代码中有关部分,比如IP地址等进行了修改,最终使程序在2台电脑上运行成功。

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