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HomeBackend DevelopmentPHP Tutorial在php中使用sockets:从新闻组中获取文章

php能打开远程或本地主机上的Socket端口。本文是一个使用Socket的小例子:连接到一个Usenet新闻组服务器,同服务器对话,从新闻组中下载一些文章。


在php中打开一个socket
使用fsockopen()打开一个socket.这个函数在php3和php4种都可以使用。函数声明是这样的:


int fsockopen (string hostname, int port _
[, int errno [, string errstr [, double timeout]]])

 
这个函数将打开一个连接到主机hostname的port端口的TCP连接。hostname可以是一个有效的域名,或者是一个ip地址。对于udp连接,你必须指定协议:udp://hostname. 对于unix域,主机名使用到socket的路径,这种情况下,端口port必须置为0。可选的timeout参数用来设定等待打开一个socket的时间,单位为秒。


关于fsockopen()的更多信息,请参考:http://www.php.net/manual/function.fsockopen.php


网络新闻传输协议
  访问新闻组服务器需要通过称为NNTP(网络新闻传输协议)的协议来进行。这个协议在rfc977中有详细的细节,可以在http://www.w3.org/PRotocols/rfc977/rfc977.html得到。这个文档分别描述了怎样连接到NNTP服务器,怎样同服务器对话,以及完成这些任务的不同命令。


连接
  连接到一个NNTP服务器需要知道它的主机名(或者是ip地址)和它侦听的端口。为了避免一个连接企图失败导致程序挂起,你应该使用timeout参数。
       $cfgServer  = "your.news.host";
    $cfgPort   = 119;
    $cfgTimeOut  = 10;

  //open a socket
    if(!$cfgTimeOut)
     // without timeout
     $usenet_handle = fsockopen($cfgServer, $cfgPort);
    else
     // with timeout
     $usenet_handle = fsockopen($cfgServer, $cfgPort, &$errno, &$errstr, $cfgTimeOut);

  if(!$usenet_handle) {
      echo "Connection failed.\n";
      exit();
    }
    else {
      echo "Connected.\n";
      $tmp = fgets($usenet_handle, 1024);
    }

?>
与服务器对话
 
现在我们已经连接到了服务器,可以通过前面打开的socket同服务器对话了。比如说我们要从某个新闻组得到最近的10篇文章。RFC977指出,第一步要用GROUP命令选择正确的新闻组:
GROUP ggg
参数ggg是要选择的新闻组的名字(比如说是"net.news"),这是必需的。可用的新闻组的列表可以用LIST命令得到。选择新闻组的命令成功后,返回组中第一篇和最后一篇文章的文章编号,以及组中文章的数目。
  

下面是一个例子:
   Chrome:~$ telnet my.news.host 119
   Trying aa.bb.cc.dd...
   Connected to my.news.host.
   Escape character is '^]'.
   200 my.news.host InterNetNews NNRP server INN 2.2.2 13-Dec-1999 ready (posting ok).
   GROUP alt.test
   211 232 222996 223235 alt.test
   quit
   205 .

   接收到命令 GROUP alt.test 后,服务器返回"211 232 222996 223235 alt.test". 211是RFC中定义的返回码,指示命令已成功执行。返回信息还指出,现在有232篇文章,最早的文章的编号是222996,最新的文章的编号是223235。我们看到,222996+232并不等于223235。丢失的7篇文章因为某种原因被从服务器删除了,可能是因为被它的合法作者取消了(这是可能的,而且很容易做到),或者因为是灌水文章而被删。
  

需要注意的事,有些服务器在选择新闻组之前可能要求身份认证,这取决于这是一个公共的或者是私用的服务器。也有可能服务器允许任何人读取文章,但发表文章需要身份验证。

      
    //$cfgUser   = "xxxxxx";
    //$cfgPasswd  = "yyyyyy";
    $cfgNewsGroup = "alt.php";

  //identification required on private server
    if($cfgUser) {
      fputs($usenet_handle, "AUTHINFO USER ".$cfgUser."n");
      $tmp = fgets($usenet_handle, 1024);
      fputs($usenet_handle, "AUTHINFO PASS ".$cfgPasswd."n");
      $tmp = fgets($usenet_handle, 1024);

    //check error
 
      if($tmp != "281 Okrn") {
        echo "502 Authentication errorn";
        exit();
      }
  }
 
  //select newsgroup
  
  fput($usenet_handle, "GROUP ".$cfgNewsGroup."n");
  $tmp = fgets($usenet_handle, 1024);
 
  if($tmp == "480 Authentication required for commandrn") {
   echo $tmp;
   exit();
  }
 
  $info = split(" ", $tmp);
  $first= $info[2];
  $last = $info[3];
 
  printf("First : %sn", $first);
  printf("Last : %lastn", $last);

?>

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