helloclient.c

linux网络程序设计 几个小程序以及编译命令

/*Hello World client*/
#include<stdio.h>
#include<stdlib.h>
#include<errno.h>
#include<string.h>
#include<sys/types.h>
#include<netinet/in.h>
#include<sys/socket.h>
#include<sys/wait.h>
#include<signal.h>
#include<arpa/inet.h>
#include<unistd.h>
#include<netinet/ip.h>
#include<netinet/ip_icmp.h>
#include<netdb.h>
#include<setjmp.h>

int main(int argc,char*argv[])
{
    int sockfd,new_fd ;
    struct sockaddr_in server_addr ;
    struct hostent*host ;
    int portnumber,nbytes ;
    char hello[]="Hello World\n" ;

    if(argc!=3)
    {
        fprintf(stderr,"Usage:%s hostname portnumber\a\n",argv[0]);
        exit(1);
    }

    if((host=gethostbyname(argv[1]))==NULL)
    {
        fprintf(stderr,"Gethostname error\n");
        exit(1);
    }
    
    if((portnumber=atoi(argv[2]))<0)
    {
        fprintf(stderr,"Usage:%s hostname portnumber\a\n",argv[0]);
        exit(1);
    }

    /* 客户程序开始建立 sockfd描述符 */
    if((sockfd=socket(AF_INET,SOCK_STREAM,0))==-1)
    {
        fprintf(stderr,"Socket Error:%s\a\n",strerror(errno));
        exit(1);
    }
    
    /* 客户程序填充服务端的资料 */
    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 */    
    if(connect(sockfd,(struct sockaddr*)(&server_addr),sizeof(struct sockaddr))==-1)
    {
        fprintf(stderr,"Connect Error:%s\a\n",strerror(errno));
        exit(1);
    }
    
    /*向服务器发消息*/
    if(write(sockfd,hello,strlen(hello))==-1)
    {
        fprintf(stderr,"Write Error:%s\n",strerror(errno));
        exit(1);
    }
    
    /* 结束通讯 */
    close(sockfd);
    exit(0);
}