CYQ’s BLOG
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ComputerWeb Experiment 2：Socket Programming

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本文用于记录计网第二次实验——套接字编程的步骤与过程。

Basic Information ｜ 基本信息

  • Device: DELL
  • System: kubuntu
  • Language: C
  • Platform: CodeBlocks

Essential Knowledge | 必备知识

  • socket()：建立socket
  • bind()：将建立的socket与本地地址绑定
  • listen()：监听可能出现的连接请求
  • accept()：接受指定socket上的连接请求
  • connect()：主动向对方发出建立连接请求
  • send()：发送消息
  • recv()：接受消息
  • close()：关闭socket

Programmes ｜ 程序代码

Server.c

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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <netdb.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <ctype.h>

#define IP "114.214.245.135"
#define MaxLine 256
#define ServerPort 6666
#define MaxPending 10

int main(void)
{
    struct sockaddr_in ServAddr, CliAddr;
    char buf[MaxLine];
    int socketfd, connfd;
    int s,new_s,len;

    //create server socket
    socketfd=socket(PF_INET,SOCK_STREAM,0);
    if ((socketfd)<0)
    {
        perror("socket");
        exit(1);
    }
    else
        printf("Socket create success!\n");

    //initializing address
    bzero((char *)&ServAddr, sizeof(ServAddr));
    ServAddr.sin_family = AF_INET;
    ServAddr.sin_addr.s_addr=inet_addr(IP);
    ServAddr.sin_port=htons(ServerPort);

    //connection
    if ((bind(socketfd, (struct sockaddr*) &ServAddr,sizeof(struct sockaddr))) == -1)
    {
        perror("bind");
        exit(1);
    }
    else
        printf("Bind success!\n");
    listen(socketfd,MaxPending);
    if(listen(socketfd,MaxPending) == -1){
        perror("listen");
        exit(1);
    }else
        printf("the server is listening!\n");

    //recving & sending
    while(1)
    {
        //chat available
        printf("*****************Start chatting***************\n");
        len = sizeof(struct sockaddr);
        if ((new_s = accept(socketfd,(struct sockaddr*) &CliAddr, &len)) == -1)
        {
            perror("simplex-talk: accept");
            exit(1);
        }
        else
            printf("You're chatting with：%s: %d\n",inet_ntoa(CliAddr.sin_addr),ntohs(CliAddr.sin_port));

        while(1)
        {
            //sending message
            memset(buf,0,sizeof(buf));
            fgets(buf,MaxLine,stdin);
            if(!strncasecmp(buf,"quit",4))
            {
                printf("Server requires quitting\n");
                break;
            }
            len = send(new_s,buf,strlen(buf),0);
            if(len > 0)
                printf("\tSend successfully：%s\n",buf);
            else
            {
                printf("Sending error\n");
                break;
            }
            //receiving message
            memset(buf,0,sizeof(buf));
            len = recv(new_s, buf, sizeof(buf),0);
            if (len>0)
                printf("Client: %s\n",buf);
            else
            {
                if(len<0)
                    printf("Receiving error");
                else
                    printf("Client quits.");
                break;
            }
        }
        printf("Chat end\n");
        close(new_s);
        break;
    }
    close(socketfd);
    return 0;
}

Client.c

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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <netdb.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <ctype.h>

#define IP "114.214.245.135"
#define MaxLine 256
#define ServerPort 6666

int main(int argc, char *argv[])
{
    FILE *fp;
    struct hostent *hp;
    struct sockaddr_in ServAddr;
    char buf[MaxLine];
    char *host;
    int s,connfd;
    int socketfd,len;

    len=sizeof(ServAddr);
    socketfd=socket(AF_INET,SOCK_STREAM,0);
    //create socket
    if(socketfd==-1)
    {
        perror("error socket");
        return -1;

    }
    printf("Socket create success!\n");

    //initializing address
    ServAddr.sin_family=AF_INET;
    ServAddr.sin_port=htons(ServerPort);
    ServAddr.sin_addr.s_addr=inet_addr(IP);

    //connection
    connfd=connect(socketfd, (struct sockaddr*)&ServAddr, sizeof(struct sockaddr));
    if(connfd == -1)
    {
        perror("connect");
        exit(1);
    }
    else
        printf("Connect success!\n");


    //chat available
    printf("*****************Start chatting***************\n");
    while(1)
    {
        //quit
        memset(buf,0,sizeof(buf));
        fgets(buf,MaxLine,stdin);
        if(!strncasecmp(buf,"quit",4))
        {
            printf("Client requires quitting\n");
            break;
        }

        //sending message
        len = send(socketfd,buf,strlen(buf),0);
        if(len > 0)
            printf("\tSend successfully：%s\n",buf);
        else
        {
            printf("Sending error\n");
            break;
        }

        //receiving message
        memset(buf,0,sizeof(buf));
        len = recv(socketfd, buf, sizeof(buf),0);
        if (len>0)
            printf("Server: %s\n",buf);
        else
        {
            if(len<0)
                printf("Receiving error");
            else
                printf("Server quits.");
            break;
        }
    }
    printf("Chat end\n");
    close(socketfd);
}

Improvements | 反思与改进

  • 无法自动读取主机IP地址，必须手动定义
  • 客户端与服务器交流时信息发送与接收的顺序会有变化，影响聊天进程