tcp流程

服务器 

头文件：

#include <sys/types.h>          /* See NOTES */
#include <sys/socket.h>
#include <errno.h>
#include<stdio.h>
#include <netinet/in.h>
#include <netinet/ip.h> /* superset of previous */
#include <arpa/inet.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>

#include <sys/types.h>          /* See NOTES */
#include <sys/socket.h>
#include <errno.h>
#include<stdio.h>
#include <netinet/in.h>
#include <netinet/ip.h> /* superset of previous */
#include <arpa/inet.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
int main(int argc, char const *argv[])
{
 if (argc != 2)
    {
        printf("usage: <port>\n");
        return -1;
    }
//1.创建套接字
    int sockfd= socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd <0 )
    {
        perror("socket err.");
        return -1;
    }
    printf("sockfd:%d\n",sockfd);
  //2.绑定ip+port
    //填充结构体
    struct sockaddr_in saddr,caddr;
    saddr.sin_family=AF_INET;//协议族
    saddr.sin_port=htons(atoi(argv[1]));//端口号
    
#if 0
    saddr.sin_addr.s_addr=inet_addr(argv[1]);//ip
#else
    //绑定电脑上的所有可用Ip给服务器
    //saddr.sin_addr.s_addr=INADDR_ANY;
    saddr.sin_addr.s_addr=inet_addr("0.0.0.0");//ip
#endif
socklen_t len=sizeof(saddr);
 if(bind(sockfd, (struct sockaddr *)&saddr,len) <0)
    {
        perror("bind err.");
        return -1; 
    }
    printf("bind success\n");
    //3.监听，将主动套接字变成被动套接字
    if(listen(sockfd, 6)<0)
    {
        perror("listen err.");
        return -1;         
    }
    printf("listen success\n");
  //4.accept阻塞等待连接产生，有连接则创建套接字。
while(1)
{
    int acceptfd=accept(sockfd, (struct sockaddr *)&caddr, &len);
    if (acceptfd<0)
    {
        perror("accept err.");
        return -1;
    }
    printf("connect ok\n");
    printf("acceptfd:%d\n",acceptfd);
    printf("ip:%s port:%d\n",inet_ntoa(caddr.sin_addr),ntohs(caddr.sin_port));
    //5.发送
#define N 64
    char buf[N]={};
    while (1)
    {
        int ret=recv(acceptfd,buf, N, 0);//返回值是实际读到的数量
        //ret的返回值有讲究，
        //当ret>0时代表对方发数据了，当ret==0时，代表对端退出，ret<0时代表接收出错
        if (ret < 0)
        {
            perror("recv err.");
            return -1;            
        }else if (ret > 0)
        {   
            printf("buf:%s\n",buf);
            memset(buf,0,N);
        }else
        {
            printf("client exit\n");
            close(acceptfd);
            break;
        }
   
    }
}
    //6.关闭套接字
    close(sockfd);
    return 0;
}
}

tcp客户端 

创建套接字socket-发送连接请求connect-发送数据（gets-send-memset）-关闭套接字close

#include <sys/types.h>          /* See NOTES */
#include <sys/socket.h>
#include <errno.h>
#include<stdio.h>
#include <netinet/in.h>
#include <netinet/ip.h> /* superset of previous */
#include <arpa/inet.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>

int main(int argc, char const *argv[])
{   
    if (argc != 3)
    {
        printf("usage:<ip> <port>\n");
        return -1;
    }
    
    //1.创建套接字
    int sockfd= socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd <0 )
    {
        perror("socket err.");
        return -1;
    }
    printf("sockfd:%d\n",sockfd);
    //2.发送连接请求
    struct sockaddr_in addr;
    addr.sin_family=AF_INET;
    addr.sin_port=htons(atoi(argv[2]));
    addr.sin_addr.s_addr=inet_addr(argv[1]);
    socklen_t addrlen=sizeof(addr);
    if(connect(sockfd, (struct sockaddr *)&addr,addrlen)<0)
    {
        perror("connect err.");
        return -1;
    }
    //3.发送数据
#define N 64
char buf[N]={0};
    while (1)
    {   
        gets(buf);
        send(sockfd,buf,N,0);
        memset(buf,0,N);
    }
    
    //4.关闭套接字
    close(sockfd);
    return 0;
}