socket 编程 简单的TCP

客户端向服务器发出连接请求后，服务器端写入数据发送给客户端，在客户端显示。

server:

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

#define MAXSIZE 1024

int main(int argc, char* argv[])
{
    int sockfd, new_fd;
    struct sockaddr_in server_addr;
    struct sockaddr_in client_addr;
    int sin_size, portnumber;
    char buf[MAXSIZE];
    if(argc != 2)
    {
        fprintf(stderr,"Usage: %s portnumbera
",argv[0]);
        exit(1);
    }
    if((portnumber = atoi(argv[1]))<0)
    {
        /*获得命令行的第二个参数端口号，atoi()把字符串转换成整形数*/
        fprintf(stderr,"usage: %s portnumbera
",argv[0]);
        exit(1);
    }
    /*服务器开始建立socket描述符*/
    sockfd = socket(AF_INET,SOCK_STREAM,0);
    
    /*服务器端填充sockaddr结构*/
    bzero(&server_addr,sizeof(struct sockaddr_in));
    server_addr.sin_family=AF_INET;
    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    server_addr.sin_port = htons(portnumber);
    
    /*调用bind函数绑定端口*/
    bind(sockfd,(struct sockaddr*)(&server_addr),sizeof(struct sockaddr));
    
    /*监听sockfd描述符，同时处理的最大链接请求数为5*/
    listen(sockfd,5);

    /*服务器阻塞，等待接收链接请求，直到客户端发送链接请求*/
    while(1)
    {
        sin_size = sizeof(struct sockaddr_in);
        /*调用accept接受一个连接请求*/
        if((new_fd = accept(sockfd,(struct sockaddr*)(&client_addr),&sin_size))==-1)
        {
            printf("accept error!
");
            exit(1);
        }
        /*TCP链接已建立，打印申请链接的客户机的IP地址*/
        printf("Server get connection from %d
",inet_ntoa(client_addr.sin_addr));
        /*提示用户输入要发送的数据，长度小于缓冲区的长度*/
        printf("Connected successful, please input the message[less than 1024 bytes]:
");
        
        /*从终端输入要发送的数据，放到buf缓冲区*/
        fgets(buf,sizeof(buf),stdin);
        
        /*调用write发送数据*/
        if(write(new_fd,buf,strlen(buf))==-1)
        {
            printf("write error!
");
            exit(1);
        }
        close(new_fd);
    }
    close(sockfd);
    return 0;
}        

client:

#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>

int main(int argc, char* argv[])
{
    int sockfd;
    char buffer[1024];
    /*定义服务器端套接口数据结构*/
    struct sockaddr_in server_addr;
    struct hostent *host;
    int portnumber, nbytes;
    if(argc!=3)
    {
        printf("Usage: %s hostname portnumbera
",argv[0]);
        exit(1);
    }
    /*获得命令行的第二个参数--主机名*/
    if((host=gethostbyname(argv[1]))==NULL)
    {
        printf("get host name error
");
        exit(1);
    }
    /*获得第三个参数，端口号*/
    if((portnumber = atoi(argv[2]))<0)
    {
        printf("port number error
");
        exit(1);
    }
    /*客户程序开始建立sockfd描述符*/
    if((sockfd = socket(AF_INET,SOCK_STREAM,0))==01)
    {
        printf("socket error
");
        exit(1);
    }
    /*客户程序填充服务端资料*/
    bzero(&server_addr,sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(portnumber);
    server_addr.sin_addr = *((struct in_addr*)host->h_addr);
    /*客户程序发起连接请求*/
    connect(sockfd,(struct sockaddr*)(&server_addr),sizeof(struct sockaddr));
    
    /*调用read读取服务器发送来的数据*/
    if((nbytes = read(sockfd,buffer,1024))==-1)
    {
        printf("read error
");
        exit(1);
    }
    buffer[nbytes] = '';
    printf("I have received:%s
",buffer);
    close(sockfd);
    return 0;
}