网络编程 简单tcp服务器/客户端_tcp通信 服务端向客户端发起请求,客户端返回给服务端当前系统时间

运用socket网络编程方法，实现简单tcp服务器和客户端交互。

功能简介：

1. 客户端发送字符串，服务器计算其长度返回
2. 客户端发送"time"命令，服务器返回自己当前时间
3. 客户端发送"get filename"命令，从服务器端下载文件

功能展示：

发送普通字符串

发送time命令

发送get命令

实现代码：

客户端实现：

/*===============================================
client.c
================================================*/
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <ctype.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <signal.h>

int main(int argc, char *argv[])
{
    if(argc != 3)
    {
        printf("Usage:%s IP Port\n",argv[0]);
        exit(-1);
    }

    //创建套接字
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if(sockfd == -1)
    {
        perror("socket");
        exit(-1);
    }

    //服务器的IP地址和端口号
    struct sockaddr_in seraddr;
    seraddr.sin_family = AF_INET;
    seraddr.sin_port = htons(atoi(argv[2]));
    //seraddr.sin_addr.s_addr = inet_addr(INADDR_ANY);
    //seraddr.sin_addr.s_addr = htonl(INADDR_ANY);
    seraddr.sin_addr.s_addr = inet_addr(argv[1]);
    socklen_t seraddr_len;

    //请求连接服务器
    if(connect(sockfd, (struct sockaddr *)&seraddr, sizeof(seraddr)) == -1)
    {
        perror("connect");
        exit(-1);
    }

    //收发数据
    char buf[64] = {0};
    char file[64] = {0};
    int n, fd1;
    char *p;

    while(1)
    {
        memset(buf, 0, sizeof(buf));
        
        //发送数据
        fgets(buf, 64, stdin);
        buf[strlen(buf)-1] = '\0';

        int m = write(sockfd, buf, 64);
        if(m < 0)
        {
            perror("writ");
            exit(-1);
        }

        //以空格分隔命令和参数
        p = buf;
        while(p[0] != ' ')  p++;
        p[0] = '\0';
        strcpy(file, p+1);

        if(strcmp(buf, "time") == 0)
        {
            //准备接收时间
            memset(buf, 0, sizeof(buf));
            if(read(sockfd, buf, 64) < 0)
            {
                perror("read");
                exit(-1);
            }
            printf("Ram:\n\ttime:%s", buf);
        }
        else if(strcmp(buf, "get") == 0)
        {
            //准备接收文件
            memset(buf, 0, sizeof(buf));
            fd1 = open(file, O_WRONLY|O_CREAT|O_TRUNC,0664);
            if(fd1 == -1)
            {
                perror("open");
                exit(-1);
            }
			
            while((n = recv(sockfd, buf, 64, 0)) > 0)
            {
            	printf("recv %d bytes\n",n);
                write(fd1, buf, n);
                memset(buf, 0, sizeof(buf));
                
                if( n < 64) break;
            }

            printf("%s receive finished...\n",file);
            close(fd1);

        }
        else
        {
            //准备接收计算的大小
            memset(buf, 0, sizeof(buf));
            if(read(sockfd, buf, 64) < 0)
            {
                perror("read");
                exit(-1);
            }
            printf("Ram\n\tsize:%s\n", buf);
        }
    }
    close(sockfd);

    return 0;
}
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服务器实现：

/*===============================================
serve.c
================================================*/
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <ctype.h>
#include <time.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <signal.h>

int main(int argc, char *argv[])
{
    if(argc != 3)
    {
        printf("Usage:%s IP Port\n",argv[0]);
        exit(-1);
    }

    //创建套接字
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if(sockfd == -1)
    {
        perror("socket");
        exit(-1);
    }
    
    //端口复用函数：解决端口号被系统占用的情况
    int on = 1;
    setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));

    //绑定服务器的IP地址和端口号
    struct sockaddr_in seraddr;
    seraddr.sin_family = AF_INET;
    seraddr.sin_port = htons(atoi(argv[2]));
    //seraddr.sin_addr.s_addr = inet_addr(INADDR_ANY);
    //seraddr.sin_addr.s_addr = htonl(INADDR_ANY);
    seraddr.sin_addr.s_addr = inet_addr(argv[1]);

    bind(sockfd, (struct sockaddr *)&seraddr, sizeof(seraddr));


    //设置监听套接字
    if(listen(sockfd, 10) == -1)
    {
        perror("listen");
        exit(-1);
    }

    //等待客户端连接
    struct sockaddr_in clientaddr = {0};//客户端地址信息
    int len_client; //客户端地址大小
    int connfd;

connect:
    connfd = accept(sockfd, (struct sockaddr *)&clientaddr,&len_client);
    if(connfd == -1)
    {
        perror("accept");
        exit(-1);
    }
    printf("connected...\n");


    char buf[64] = {0};
    int n, len, fd1;
    char file[64] = {0};
    time_t now_time;
    char *p;

    //收发数据
    while(1)
    {
        memset(buf, 0, sizeof(buf));

        //接收数据
        int m = read(connfd, buf, 64);
        if(m < 0)
        {
            perror("read");
            exit(-1);
        }
        else if(m == 0)//客户端关闭 未读到数据
        {
            printf("waiting connection...\n");
            close(connfd);
            goto connect;
            //break;
        }
        printf("Rem:\n\t%s\n",buf);

        //以空格分隔命令和参数
        p = buf;
        while(p[0] != ' ')  p++;
        p[0] = '\0';
        strcpy(file, p+1);

        if(strcmp(buf,"time") == 0)
        {
            //发送当前系统时间
            memset(buf, 0, sizeof(buf));
            now_time = time(NULL);
            strcpy(buf, ctime(&now_time));
            if(write(connfd, buf, 64) < 0)
            {
                perror("write");
                exit(-1);
            }
            
        }
        else if(strcmp(buf, "get") == 0)
        {
            //发送文件
            memset(buf, 0, sizeof(buf));
            fd1 = open(file, O_RDONLY);
            if(fd1 == -1)
            {
                perror("open");
                exit(-1);
            }

            while((n = read(fd1, buf, 64)) > 0)
            {
            	printf("read %d bytes\n",n);
                write(connfd, buf, n);
                memset(buf, 0, sizeof(buf));
            }
            
            printf("%s send finished...\n",file);
            close(fd1);
        }
        else
        {
            //发送接收到的数据字节大小
            len = strlen(buf);
            memset(buf, 0, sizeof(buf));
            sprintf(buf, "%d", len);
            if(write(connfd, buf, 64) < 0)
            {
                perror("write");
                exit(-1);
            }
        }

    }

    close(sockfd);
    close(connfd);

    return 0;
}
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