Linux基础知识：系统创建TCP连接流程介绍

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <pthread.h>
#include <time.h>
#define MAXSIZE 128

char news[MAXSIZE];
int res;            //用以接收函数返回值

void* pthread_chat(void * arg)      //创建线程用以接收数据
{
    int confd = *(int *)arg;
    while(1)
    {
        res  = recv(confd, news, sizeof(news), 0);
        if(res <= 0)
        {
        perror("recv");
        break;
        }
        printf("The news is: %s\n",news);
        memset(news,0,MAXSIZE);
        send(confd,"OK",2,0);
    }

    printf("One client over\n");
    close(confd);
}

char *Time()                    //获取当前时间
{
    time_t timer;
    struct tm *tblock;
    timer = time(NULL);
    tblock = localtime(&timer);
    return asctime(tblock);
}

void save(char *s)              //储存日志文件
{
    int fd;
    fd = open("journal",O_RDWR|O_APPEND|O_CREAT);

    if(fd < 0)
        perror("open");
    else
    {
        char *buf = Time();
        strcat(buf,s);

        write(fd,buf,MAXSIZE);
        lseek(fd,0,SEEK_END);

        if(res < 0)
            perror("write");
    }
}

int main()
{
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    struct sockaddr_in saddr, caddr;
    saddr.sin_family = AF_INET;
    saddr.sin_port = htons(6666);
    saddr.sin_addr.s_addr = inet_addr("127.0.0.1");

    res = bind(sockfd,(struct sockaddr*)&saddr, sizeof(saddr));
    if(res < 0)
        perror("bind");

    listen(sockfd, 5);          //监听端口

    while(1)
    {
        int len = sizeof(caddr);
        int confd = accept(sockfd,(struct sockaddr*)&caddr, &len);
        if(confd < 0)
        {
            perror("accept");
            continue;
        }else
        {
            save(inet_ntoa(caddr.sin_addr));
        }

        printf("Accept confdis:%d, ip=%s\n",confd,inet_ntoa(caddr.sin_addr));

        pthread_t tid;
        pthread_create(&tid, NULL, pthread_chat, &confd);
    }
}

#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>  
#define MAXSIZE 128

char news[MAXSIZE];
int res;                    //用来接收函数返回值
int main()
{
    printf("------Welcome join the chat room-----\n");
    printf("If you want to quit,please input --bye--\n");
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);

    struct sockaddr_in saddr;
    saddr.sin_family = AF_INET;
    saddr.sin_port = htons(6666);
    saddr.sin_addr.s_addr = inet_addr("127.0.0.1");

    int confd = connect(sockfd,(struct sockaddr*)&saddr,sizeof(saddr));
    if(confd < 0)
        perror("connect");

    while(1)
    {
        printf("Please input the news\n");
        fgets(news,MAXSIZE,stdin);

        if(strncmp(news,"bye",3) == 0)
        {
            break;
        }

        send(sockfd, news, strlen(news), 0);
        memset(news,0,MAXSIZE);
        recv(sockfd, news, sizeof(news), 0);
          printf("The serve's news is: %s\n",news);
    }

    close(sockfd);
    exit(0);
}