C语言socket编程

建议先去看一下思路

真的写的很不错呦~

思路参考博客：https://www.cnblogs.com/renfanzi/p/5713054.html

linux c语言socket编程代码（单一服务端与客户端） 【此代码有bug，但很方便理解，用于理解使用】： 

代码参考博客：https://www.cnblogs.com/xudong-bupt/p/3483059.html

服务端代码：

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

#define MYPORT  8887
#define QUEUE   20
#define BUFFER_SIZE 1024

int main() {
    // 实例化socket对象， 定义sockfd
    /* AF_INET 默认为IPv4
     * SOCK_STREAM 流式socket， for TCP
     * 0 协议， 默认选择合适的协议
     * */
    int server_sockfd = socket(AF_INET, SOCK_STREAM, 0);

    ///定义sockaddr_in
    struct sockaddr_in server_sockaddr;
    server_sockaddr.sin_family = AF_INET;
    server_sockaddr.sin_port = htons(MYPORT);
    server_sockaddr.sin_addr.s_addr = htonl(INADDR_ANY);

    // 将套接字绑定到地址
    // bind，成功返回0，出错返回-1
    if (bind(server_sockfd, (struct sockaddr *) &server_sockaddr, sizeof(server_sockaddr)) == -1) {
        perror("bind");
        exit(1);
    }

    // 监听
    // listen，成功返回0，出错返回-1
    if (listen(server_sockfd, QUEUE) == -1) {
        perror("listen");
        exit(1);
    }

    // 客户端套接字
    char buffer[BUFFER_SIZE];
    struct sockaddr_in client_addr;
    socklen_t length = sizeof(client_addr);

    // 进入阻塞状态，等待客户连接
    // 成功返回非负描述字，出错返回-1
    int conn = accept(server_sockfd, (struct sockaddr *) &client_addr, &length);
    if (conn < 0) {
        perror("connect");
        exit(1);
    }
    // 循环
    while (1) {
        memset(buffer, 0, sizeof(buffer));
        // 接受消息
        int len = recv(conn, buffer, sizeof(buffer), 0);
        printf("len: %d
", len); 
        //这里是一直循环的，如果客户端说一句话，然后结束以后，这里一直循环，需要注意
        
        if (strcmp(buffer, "exit
") == 0)
            break;
        fputs(buffer, stdout);
        // 发送消息
        send(conn, "hehe", 5, 0);
    }
    close(conn);
    close(server_sockfd);
    return 0;
}

客户端代码：

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

#define MYPORT  8887
#define BUFFER_SIZE 1024

int main()
{
    ///定义sockfd
    int sock_cli = socket(AF_INET,SOCK_STREAM, 0);

    ///定义sockaddr_in
    struct sockaddr_in servaddr;
    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(MYPORT);  ///服务器端口
    servaddr.sin_addr.s_addr = inet_addr("127.0.0.1");  ///服务器ip

    ///连接服务器，成功返回0，错误返回-1
    if (connect(sock_cli, (struct sockaddr *)&servaddr, sizeof(servaddr)) < 0)
    {
        perror("connect");
        exit(1);
    }

    char sendbuf[BUFFER_SIZE];
    char recvbuf[BUFFER_SIZE];
    while (fgets(sendbuf, sizeof(sendbuf), stdin) != NULL)
    {
        send(sock_cli, sendbuf, strlen(sendbuf),0); ///发送
        if(strcmp(sendbuf,"exit
")==0)
            break;
        recv(sock_cli, recvbuf, sizeof(recvbuf),0); ///接收
        fputs(recvbuf, stdout);

        memset(sendbuf, 0, sizeof(sendbuf));
        memset(recvbuf, 0, sizeof(recvbuf));
    }

    close(sock_cli);
    return 0;
}

采用C/S架构，Tcp、Ip协议，服务器端使用共享内存的方式，不同客户端连接服务端，实现网络聊天室的功能（多用户）

服务端：

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h> //数据类型定义
#include <sys/stat.h> //文件属性
#include <netinet/in.h> //定义数据结构sockaddr_in
#include <sys/socket.h> //提供socket函数和数据结构
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <sys/ipc.h>
#include <errno.h>
#include <sys/shm.h> //共享内存
#include <time.h>
#include<sys/time.h>
#include <arpa/inet.h>

#define PERM S_IRUSR | S_IWUSR //用户读写
#define MYPORT  8080 //通信端口
#define BACKLOG 10 //定义服务器段可以连接的最大客户数
#define MYHOST  "192.168.2.137"
#define WELCOME "|---------------Welcome to the chat room!----------------|"//当客户端连接服务端时，向客户端发送此字符串

//将int类型转换成char*类型
void itoa(int i, char *string) {
    int mask = 1;
    while (i / mask >= 10)
        mask *= 10;
    while (mask > 0) {
        *string++ = i / mask + '0';
        i %= mask;
        mask /= 10;
    }
    *string = '';
}

//得到当前系统的时间
void get_cur_time(char *time_str) {
    struct timeval now;
    gettimeofday(&now, NULL);
    strcpy(time_str, ctime(&now.tv_sec));
}

//创建共享存储区
int shm_create() {
    int shmid;
    //shmid = shmget(IPC_PRIVATE, 1024, PERM);
    if ((shmid = shmget(IPC_PRIVATE, 1024, PERM)) == -1) {
        fprintf(stderr, "Create Share Memory Error:%s
a", strerror(errno));
        exit(1);
    }
    return shmid;
}

//端口绑定函数。创建套接字，并绑定到指定端口
int bindPort(unsigned short int port) {
    int sockfd;
    struct sockaddr_in my_addr;
    sockfd = socket(AF_INET, SOCK_STREAM, 0); //创建基于流套接字
    //bzero(&(my_addr.sin_zero),0);
    bzero(&my_addr, sizeof(my_addr));
    my_addr.sin_family = AF_INET; //IPV4协议族
    my_addr.sin_port = htons(port); //转换端口为网络字节序
    my_addr.sin_addr.s_addr = inet_addr(MYHOST);

    if (bind(sockfd, (struct sockaddr *) &my_addr, sizeof(struct sockaddr)) == -1) {
        perror("fail to bind");
        exit(1);
    }

    printf("bind success!
");
    return sockfd;
}

int main(int argc, char *argv[]) {
    int sockfd, clientfd; //监听套接字、客户套接字
    int sin_size, recvbytes;

    pid_t pid, ppid; //定义父子进程标记
    char *buf, *read_addr, *write_addr, *temp, *time_str; //需要用到的缓冲区
    struct sockaddr_in their_addr; //定义地址结构
    int shmid;

    shmid = shm_create(); //创建共享存储区

    temp = (char *) malloc(255);
    time_str = (char *) malloc(50);
    sockfd = bindPort(MYPORT); //绑定端口

    get_cur_time(time_str);
    printf("Time is : %s
", time_str);

    if (listen(sockfd, BACKLOG) == -1) {
        //在指定端口上监听
        perror("fail to listen");
        exit(1);
    }

    printf("listen....
");
    while (1) {
        /*
        if (listen(sockfd, BACKLOG) == -1)
        {
            perror("fail to listen");
            exit(1);
        }
        */
        //接受一个客户端的连接请求
        if ((clientfd = accept(sockfd, (struct sockaddr *) &their_addr, &sin_size)) == -1) {
            perror("fail to accept");
            exit(1);
        }

        //得到客户端的IP地址输出
        char address[20];
        inet_ntop(AF_INET, &their_addr.sin_addr, address, sizeof(address));

        printf("accept from %s
", address);
        send(clientfd, WELCOME, strlen(WELCOME), 0); //发送问候信息
        buf = (char *) malloc(255);

        ppid = fork(); //创建子进程
        if (ppid == 0) //子进程
        {
            pid = fork(); //子进程创建子进程
            while (1) {
                if (pid > 0) {
                    //buf = (char *)malloc(255);
                    //父进程用于接收信息
                    memset(buf, 0, 255);
                    printf("OK
");
                    if ((recvbytes = recv(clientfd, buf, 255, 0)) <= 0) {
                        perror("fail to recv");
                        close(clientfd);
                        raise(SIGKILL);
                        exit(1);
                    }
                    write_addr = shmat(shmid, 0, 0); //shmat将shmid所代表的全局的共享存储区关联到本进程的进程空间
                    memset(write_addr, '', 1024);

                    //把接收到的消息存入共享存储区中
                    strncpy(write_addr, buf, 1024);

                    //把接收到的消息连接此刻的时间字符串输出到标准输出
                    get_cur_time(time_str);
                    strcat(buf, time_str);
                    printf(" %s
", buf);
                } else if (pid == 0) {
                    //子进程用于发送消息
                    sleep(1); //子进程先等待父进程把接收到的信息存入共享存储区
                    read_addr = shmat(shmid, 0, 0); //读取共享存储区的内容

                    //temp存储上次读取过的内容,每次先判断是否已经读取过该消息
                    if (strcmp(temp, read_addr) != 0) {
                        strcpy(temp, read_addr); //更新temp，表示已经读取过该消息

                        get_cur_time(time_str);
                        strcat(read_addr, time_str);
                        if (send(clientfd, read_addr, strlen(read_addr), 0) == -1) {
                            perror("fail to send");
                            exit(1);
                        }
                        memset(read_addr, '', 1024);
                        strcpy(read_addr, temp);
                    }
                } else
                    perror("fai to fork");
            }
        }
    }
    printf("------------------------------------
");
    free(buf);
    close(sockfd);
    close(clientfd);
    return 0;
}

客户端二、客户端三...

#include <stdio.h>
#include <netinet/in.h> //定义数据结构sockaddr_in
#include <sys/socket.h> //定义socket函数以及数据结构
#include <sys/types.h>
#include <string.h>
#include <stdlib.h>
#include <netdb.h>
#include <unistd.h>
#include <signal.h>
#include <time.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#define MYPORT  8080
#define MYHOST  "192.168.2.137"



int main(int argc, char *argv[])
{
    struct sockaddr_in clientaddr; //定义地址结构
    pid_t pid;
    int clientfd, sendbytes, recvbytes;
    struct hostent *host; //主机信息数据结构
    char *buf, *buf_read;
//    if (argc < 4)
//    {
//        printf("wrong usage");
//        printf("%s host port name
", argv[0]);
//        exit(1);
//    }
//    host = gethostbyname(argv[1]);
    if ((clientfd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
    {
        perror("fail to create socket");
        exit(1);
    }
    bzero(&clientaddr, sizeof(clientaddr));
    clientaddr.sin_family = AF_INET;
    clientaddr.sin_port = htons(MYPORT);
    clientaddr.sin_addr.s_addr = inet_addr(MYHOST);
    //客户端连接服务端
    if (connect(clientfd, (struct sockaddr *)&clientaddr, sizeof(struct sockaddr)) == -1)
    {
        perror("fail to connect");
        exit(1);
    }
    buf = (char *)malloc(120);
    memset(buf, 0, 120);
    buf_read = (char *)malloc(100);

    if (recv(clientfd, buf, 100, 0) == -1)
    {
        perror("fail to recv");
        exit(1);
    }
    printf("
%s
", buf);
    pid = fork();
    while (1)
    {
        if (pid > 0)
        {
            //父进程发送消息
            strcpy(buf, "afsasdf");
            strcat(buf, ":");
            memset(buf_read, 0, 100);
            fgets(buf_read, 100, stdin);
            strncat(buf, buf_read, strlen(buf_read) - 1);
            if ((sendbytes = send(clientfd, buf, strlen(buf), 0)) == -1)
            {
                perror("fail to send");
                exit(1);
            }
        }
        else if (pid == 0)
        {
            //子进程接受消息
            memset(buf, 0, 100);
            if (recv(clientfd, buf, 100, 0) <= 0)
            {
                perror("fail to recv");
                close(clientfd);
                raise(SIGSTOP);
                exit(1);
            }
            printf("%s
", buf);
        }
        else
            perror("fork error");
    }
    close(clientfd);
    return 0;
}