1 简介

#include "unp.h"
int main(int argc,char **argv){
    int sockfd.n;
    char recvline[MAXLINE + 1];
    struct sockaddr_in servaddr;
    if(argc != 2 )
        err_quit("usage:a.out<IP address>");
    if((sockfd = socket(AF_INET,SOCK_STREAM,0)) < 0)
        err_sys("socket error");
    bzero(&servaddr,sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(13);
    if( inet_pton(AF_INET,argv[1],&servaddr.sin_addr) <= 0)
        err_quit("inet_pton error for %s",argv[1]);
    if( connect(sockfd,(SA *) &servaddr,sizeof(servaddr)) < 0)
        err_sys("connect error");
    while( (n = read(sockfd,recvline,MAXLINE)) > 0){
        recvline[n] = 0;
        if(fputs(recvline,stdout) == EOF)
            err_sys("fputs error");
    }
    if(n<0)
        err_sys("read error");
    exit(0);
}

netstat -ni 显示网络接口
netstat -r 路由表信息
ifconfig 输出IP地址信息