Linux C编程(4) 基本网络编程

一、得到主机名及其它基本信息

1.源代码

#include <stdio.h>#include <sys/utsname.h>int main(){        int res;        struct utsname netInfo;        res = uname(&netInfo);        if(-1 == res)        {                printf("call unmae failed\n");                return 0;        }        else                printf("System name:%s\nNodename:%s\nRelease:%s\nVersion:%s\nMachine:%s\n",                        netInfo.sysname, netInfo.nodename, netInfo.release, netInfo.version, netInfo.machine);        return 0;}

      结果如下:

      System name:Linux
      Nodename:GH98678
      Release:3.2.0-29-generic
      Version:#46-Ubuntu SMP Fri Jul 27 17:03:23 UTC 2012
      Machine:x86_64
2.解释

struct utsname{    char sysname[SYS_NMLN];        //使用的操作系统名，如：linux    char nodename[SYS_NMLN];        //网络结点主机名     char release[SYS_NMLN];        //操作系统的发布，如：linux内核为2.2.10，则为"2.2.10"    char version[SYS_NMLN];        //操作系统的版本，对于linux代表内核版本，日期     char machine[SYS_NMLN];        //主机的硬件类型，如i386    ......  } //返回值： //调用成功：0，失败：-1，错误原因记录在errno中

二、由主机名得到IP地址

1.源代码

#include <netdb.h>#include <string.h>#include <stdio.h>int main(int argc, char * argv[]){        if(argc != 2)        {                printf("please input domain name\n");                return 1;        }        struct hostent * ht = gethostbyname(argv[1]);        if(!ht)                printf("cann't get host information\n");        int i=0;        printf("Host:%s\n", argv[1]);        printf("Name:%s\n", ht->h_name);        printf("Type:%s\n", ht->h_addrtype==AF_INET?"AF_INET":"AF_INET6");        printf("IP Lenth:%d\n", ht->h_length);        printf("\nIP Address:\n");        char **pptr = 0;        char ipStr[80];        pptr = ht->h_addr_list;        for(;*pptr != NULL; pptr++)        {                inet_ntop(ht->h_addrtype, *pptr, ipStr, sizeof(ipStr));                printf("address:%s\n", ipStr);        }        return 1;}

设程序名为testhost。 按下面所示，运动此程序。

./testhost www.google.com

结果如下

Host:www.google.comName:www.google.comType:AF_INETIP Lenth:4IP Address:address:74.125.31.147address:74.125.31.99address:74.125.31.103address:74.125.31.104address:74.125.31.105address:74.125.31.106

2.解释

      主函数参数解释

      int  main(int argc,  char* argv[])  
      argc是命令行总的参数个数+1
      argv保存了程序名和命令行输入的每个参数。其中argv[0]为程序名。【1】
      如下例

#include <string.h>#include <stdio.h>int main(int argc, char * argv[]){        printf("application name is:%s\n", argv[0]);        int i;        for(i=1; i<argc; i++)        {                printf("%s\n", argv[i]);        }        return 1;}

      我们在命令行执行此程序，后面不跟参数
      ./testhost
      输出结果如下：
      application name is:./testhost
      我们在程序后面添加参数。参数之间以空格隔开。
      ./testhost linux windows qq wps
      输出结果如下

application name is:./testhostlinuxwindowsqqwps

 

三、简单的服务端Socket程序

1.源代码

    实现功能:向服务端发送消息，服务端打印消息，向客户端回馈消息。

#include <sys/types.h>#include <sys/socket.h>#include <stdio.h>#include <netinet/in.h>#include <arpa/inet.h>#include <unistd.h>#define TK_PORT 3339 #define MAX_BUFFER_SIZE 80 #define RECV_MSG "thanks"int main(){ int tcp_server_socket = socket(PF_INET, SOCK_STREAM, 0); //<bind> struct sockaddr_in address; memset(&address, 0, sizeof(address)); address.sin_family = PF_INET; //convert to network byte order address.sin_addr.s_addr = htonl(INADDR_ANY); address.sin_port = htons(TK_PORT);  int retBind = bind(tcp_server_socket, (struct sockaddr *)&address, sizeof(address) ); if(-1 == retBind) {  printf("bind error\n");  exit(0); } //</bind> //set passive socket printf("listening ...\n"); listen(tcp_server_socket, 10 ); struct sockaddr_in address2; socklen_t addressLen = sizeof(address2); printf("accepting ...\n"); //如果等待连接队列为空 则阻塞，等待连接。 //accept 返回一个socket，可用这个socket向客户端发消息。 int clientSocket = accept(tcp_server_socket, (struct sockaddr*)&address2, &addressLen); if( -1 == clientSocket) {  printf("accept error\n");  exit(0); }  printf("while ...\n");  //Receive char buffer[MAX_BUFFER_SIZE]; ssize_t recvSize; ssize_t setSize; //int i = 0; //for(i=0;i<100;i++) while(1) {  printf("waiting recv ...\n ");  sleep(1);  //fflush(stdout);  //recv 阻塞 直到接到消息  recvSize = recv(clientSocket, buffer, MAX_BUFFER_SIZE-1,0 );  buffer[recvSize] = '\0';  if(0 == recvSize)   //客户端断开时 返回0  {   printf("bye, server\n");   break;  }  printf("Received %d bytes:%s\n", recvSize, buffer);  send(clientSocket, RECV_MSG, strlen(RECV_MSG), 0);   } close(clientSocket); //关闭资源 return 0;} 

2.测试方法

   运行此程序。程序名为ts示:please wait a moment!

   运行netstat -a 查看此程序是否运行及占用端口。

   使用TCP调试助手，向服务端42.121.5.59发送消息

点手动发送后，服务器显示"est socket"数据接收区显示"thanks"。

 

参考文档

【1】http://blog.csdn.net/lambol_8309/article/details/4524964