PHP fsockopen函数说明：

Open Internet or Unix domain socket connection（打开套接字链接）

Initiates a socket connection to the resource specified by target .

fsockopen() returns a file pointer which may be used together with the other file functions (such as fgets() , fgetss() , fwrite() , fclose() , and feof() ).就是返回一个文件句柄

开启PHP fsockopen这个函数

PHP fsockopen需要 PHP.ini 中 allow_url_fopen 选项开启

例子如下：

1. $fp = fsockopen("www.example.com",
   80, $errno, $errstr, 30);

2. if (!$fp) {

3. echo "$errstr ($errno)<br/>\n";

4. } else {

5. $out = "GET / HTTP/1.1\r\n";

6. $out .= "Host: www.example.com\r\n";

7. $out .= "Connection: Close\r\n\r\n";

8. fwrite($fp, $out);

9. while (!feof($fp)) {

10. echo fgets($fp, 128);

11. }

12. fclose($fp);

13. }
    

处理下载问题时，所用到的方法

function downloadFile($file) {
 $host = '********';

 $out = "GET $file HTTP/1.0\r\n";
 $out .= "Host: $host\r\n";
 $out .= "Connection: Close\r\n\r\n";

 $fp = fsockopen($host, 80);
 fwrite($fp, $out);

 $headers = array();
 $body = '';
 $filenameExt = '';
 $isBody = false;
 while(true) {
   $line = fgets($fp);
   if (false === $line) {
     break;
   }
   if ($line == "\r\n") {
     $isBody = true;
     continue;
   }

   if ($isBody) {
     $body .= $line;
     echo strlen($body) . " ... \r";
   } else {
     if (strpos($line, 'filename')) {
       preg_match('!filename="(.+?)\.([\w]+)"!', $line, $filename);
       $filenameExt = $filename[2];
     }
     $headers[] = trim($line);
   }
 }
 fclose($fp);

 return array('fileExt' => $filenameExt, 'headers' => $headers, 'body' => $body);
}