我可以找到很多关于长轮询如何工作的信息(例如,这个和这个),但没有简单的例子说明如何在代码中实现这一点。

我能找到的只有cometd,它依赖DojoJS框架和一个相当复杂的服务器系统。。

基本上,我将如何使用Apache来服务请求,以及我将如何编写一个简单的脚本(例如,用PHP)来“长轮询”服务器以获取新消息?

该示例不一定是可扩展的、安全的或完整的,它只需要工作即可!


当前回答

这里是Erik Dubelboer使用Content类型:multipart/x-mixed-replace-header在PHP中的一个简单的长轮询示例:

<?

header('Content-type: multipart/x-mixed-replace; boundary=endofsection');

// Keep in mind that the empty line is important to separate the headers
// from the content.
echo 'Content-type: text/plain

After 5 seconds this will go away and a cat will appear...
--endofsection
';
flush(); // Don't forget to flush the content to the browser.


sleep(5);


echo 'Content-type: image/jpg

';

$stream = fopen('cat.jpg', 'rb');
fpassthru($stream);
fclose($stream);

echo '
--endofsection
';

下面是一个演示:

http://dubbelboer.com/multipart.php

其他回答

谢谢你的代码,dbr。只有long_poller.htm中的一个小错别字

1000 /* ..after 1 seconds */

我想应该是

"1000"); /* ..after 1 seconds */

让它发挥作用。

对于那些感兴趣的人,我尝试了Django的等效版本。开始一个新的Django项目,比如说长轮询:

django-admin.py startproject lp

调用消息服务器的应用程序msgsrv:

python manage.py startapp msgsrv

将以下行添加到settings.py以创建模板目录:

import os.path
PROJECT_DIR = os.path.dirname(__file__)
TEMPLATE_DIRS = (
    os.path.join(PROJECT_DIR, 'templates'),
)

在urls.py中定义URL模式如下:

from django.views.generic.simple import direct_to_template
from lp.msgsrv.views import retmsg

urlpatterns = patterns('',
    (r'^msgsrv\.php$', retmsg),
    (r'^long_poller\.htm$', direct_to_template, {'template': 'long_poller.htm'}),
)

msgsrv/views.py应该如下所示:

from random import randint
from time import sleep
from django.http import HttpResponse, HttpResponseNotFound

def retmsg(request):
    if randint(1,3) == 1:
        return HttpResponseNotFound('<h1>Page not found</h1>')
    else:
        sleep(randint(2,10))
        return HttpResponse('Hi! Have a random number: %s' % str(randint(1,10)))

最后,templates/long_poller.htm应与上面相同,并更正了拼写错误。希望这有帮助。

我有一个非常简单的聊天示例作为晃动的一部分。

编辑:(因为每个人都在这里粘贴代码)

这是使用长轮询和晃动的完整的基于JSON的多用户聊天。这是一个如何进行调用的演示,因此请忽略XSS问题。任何人都不应该在不首先清理它的情况下部署它。

请注意,客户端始终与服务器保持连接,一旦有人发送消息,每个人都应该立即大致看到。

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<!-- Copyright (c) 2008 Dustin Sallings <dustin+html@spy.net> -->
<html lang="en">
  <head>
    <title>slosh chat</title>
    <script type="text/javascript"
      src="http://code.jquery.com/jquery-latest.js"></script>
    <link title="Default" rel="stylesheet" media="screen" href="style.css" />
  </head>

  <body>
    <h1>Welcome to Slosh Chat</h1>

    <div id="messages">
      <div>
        <span class="from">First!:</span>
        <span class="msg">Welcome to chat. Please don't hurt each other.</span>
      </div>
    </div>

    <form method="post" action="#">
      <div>Nick: <input id='from' type="text" name="from"/></div>
      <div>Message:</div>
      <div><textarea id='msg' name="msg"></textarea></div>
      <div><input type="submit" value="Say it" id="submit"/></div>
    </form>

    <script type="text/javascript">
      function gotData(json, st) {
        var msgs=$('#messages');
        $.each(json.res, function(idx, p) {
          var from = p.from[0]
          var msg = p.msg[0]
          msgs.append("<div><span class='from'>" + from + ":</span>" +
            " <span class='msg'>" + msg + "</span></div>");
        });
        // The jQuery wrapped msgs above does not work here.
        var msgs=document.getElementById("messages");
        msgs.scrollTop = msgs.scrollHeight;
      }

      function getNewComments() {
        $.getJSON('/topics/chat.json', gotData);
      }

      $(document).ready(function() {
        $(document).ajaxStop(getNewComments);
        $("form").submit(function() {
          $.post('/topics/chat', $('form').serialize());
          return false;
        });
        getNewComments();
      });
    </script>
  </body>
</html>

这里是Erik Dubelboer使用Content类型:multipart/x-mixed-replace-header在PHP中的一个简单的长轮询示例:

<?

header('Content-type: multipart/x-mixed-replace; boundary=endofsection');

// Keep in mind that the empty line is important to separate the headers
// from the content.
echo 'Content-type: text/plain

After 5 seconds this will go away and a cat will appear...
--endofsection
';
flush(); // Don't forget to flush the content to the browser.


sleep(5);


echo 'Content-type: image/jpg

';

$stream = fopen('cat.jpg', 'rb');
fpassthru($stream);
fclose($stream);

echo '
--endofsection
';

下面是一个演示:

http://dubbelboer.com/multipart.php

最简单的NodeJS

const http = require('http');

const server = http.createServer((req, res) => {
  SomeVeryLongAction(res);
});

server.on('clientError', (err, socket) => {
  socket.end('HTTP/1.1 400 Bad Request\r\n\r\n');
});

server.listen(8000);

// the long running task - simplified to setTimeout here
// but can be async, wait from websocket service - whatever really
function SomeVeryLongAction(response) {
  setTimeout(response.end, 10000);
}

在Express for exmaple的生产方面的场景中,您将在中间件中得到响应。做您需要做的事情,可以将所有长轮询方法的范围扩展到Map或其他流(对其他流可见),并在准备就绪时调用<Response>Response.end()。长轮询连接没有什么特别之处。休息只是您通常构建应用程序的方式。

如果你不知道我所说的范围界定是什么意思,这会让你明白

const http = require('http');
var responsesArray = [];

const server = http.createServer((req, res) => {
  // not dealing with connection
  // put it on stack (array in this case)
  responsesArray.push(res);
  // end this is where normal api flow ends
});

server.on('clientError', (err, socket) => {
  socket.end('HTTP/1.1 400 Bad Request\r\n\r\n');
});

// and eventually when we are ready to resolve
// that if is there just to ensure you actually 
// called endpoint before the timeout kicks in
function SomeVeryLongAction() {
  if ( responsesArray.length ) {
    let localResponse = responsesArray.shift();
    localResponse.end();
  }
}

// simulate some action out of endpoint flow
setTimeout(SomeVeryLongAction, 10000);
server.listen(8000);

正如你所看到的,你真的可以对所有的联系做出反应,一是做任何你想做的事。每个请求都有id,因此您应该能够使用map和访问特定的api外调用。

下面是我为Inform8 Web开发的一个长轮询解决方案。基本上,重写类并实现loadData方法。当loadData返回值或操作超时时,它将打印结果并返回。

如果脚本的处理时间可能超过30秒,则可能需要将set_time_limit()调用更改为更长的时间。

Apache 2.0许可证。github上的最新版本https://github.com/ryanhend/Inform8/blob/master/Inform8-web/src/config/lib/Inform8/longpoll/LongPoller.php

Ryan

abstract class LongPoller {

  protected $sleepTime = 5;
  protected $timeoutTime = 30;

  function __construct() {
  }


  function setTimeout($timeout) {
    $this->timeoutTime = $timeout;
  }

  function setSleep($sleep) {
    $this->sleepTime = $sleepTime;
  }


  public function run() {
    $data = NULL;
    $timeout = 0;

    set_time_limit($this->timeoutTime + $this->sleepTime + 15);

    //Query database for data
    while($data == NULL && $timeout < $this->timeoutTime) {
      $data = $this->loadData();
      if($data == NULL){

        //No new orders, flush to notify php still alive
        flush();

        //Wait for new Messages
        sleep($this->sleepTime);
        $timeout += $this->sleepTime;
      }else{
        echo $data;
        flush();
      }
    }

  }


  protected abstract function loadData();

}