blocks|key|42004|text|您可以使用http.listen方法，该方法有一个回调函数，在服务器准备就绪时触发：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|42005|http.createServer(app).listen(app.get('port'),+function+()+{
++++console.log('Printed+when+ready!!!');
});|code-block|syntax|javascript|42006|请参阅Node.js上的官方参考：|42007|http://nodejs.org/api/all.html#all_server_listen_port_hostname_backlog_callback|42008|http://nodejs.org/api/all.html#all_server_listen_path_callback_1|42009|http://nodejs.org/api/all.html#all_server_listen_handle_callback_1|42010|entityMap|0|LINK|mutability|MUTABLE|url|1|2^0|5|B|0|0|0|0|27|0|0|0|1S|1|0|0|1U|2|0^^$0|@$1|2|3|4|5|6|7|11|8|@$9|12|A|13|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|14|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|15|8|@]|D|@]|E|$]]|$1|M|3|N|5|6|7|16|8|@]|D|@$9|17|A|18|1|19]]|E|$]]|$1|O|3|P|5|6|7|1A|8|@]|D|@$9|1B|A|1C|1|1D]]|E|$]]|$1|Q|3|R|5|6|7|1E|8|@]|D|@$9|1F|A|1G|1|1H]]|E|$]]|$1|S|3|-4|5|6|7|1I|8|@]|D|@]|E|$]]]|T|$U|$5|V|W|X|E|$Y|N]]|Z|$5|V|W|X|E|$Y|P]]|10|$5|V|W|X|E|$Y|R]]]]

You can use the <code>http.listen</code> method which has a callback function that triggers once the server is ready:

<pre><code>http.createServer(app).listen(app.get('port'), function () {
 console.log('Printed when ready!!!');
});
</code></pre>

See the official reference at Node.js:

<a href="http://nodejs.org/api/all.html#all_server_listen_port_hostname_backlog_callback" rel="nofollow noreferrer">http://nodejs.org/api/all.html#all_server_listen_port_hostname_backlog_callback</a>

<a href="http://nodejs.org/api/all.html#all_server_listen_path_callback_1" rel="nofollow noreferrer">http://nodejs.org/api/all.html#all_server_listen_path_callback_1</a>

<a href="http://nodejs.org/api/all.html#all_server_listen_handle_callback_1" rel="nofollow noreferrer">http://nodejs.org/api/all.html#all_server_listen_handle_callback_1</a>

blocks|key|258932|text|正如许多人提到的，listen函数(在express应用程序或http服务器上，两者都支持它)确实支持回调，这将让您的节点进程知道它何时正在侦听。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|258933|因此，如果你计划在express应用程序中启动浏览器，那么在那里就可以了。但是，如果您从外部脚本启动express应用程序，然后希望该外部脚本打开浏览器，那么节点回调并不会真正为您带来任何好处。|258934|在stdout上等待一些神奇的字符串并不是仅仅等待一个好的HTTP响应的真正改进。在获得成功响应之前，您也可以对curl使用try/backoff/timeout循环。|258935|entityMap^0|9|6|0|0|1K|4|0^^$0|@$1|2|3|4|5|6|7|L|8|@$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|O|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|P|8|@$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|J|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|K|$]]

As many have mentioned, the <code>listen</code> function (on the express app or an http server, both support it), does support a callback and that will let your node process know when it is listening.

So if you plan to launch the browser from within your express app, do it there and you are good. However, if you are launching the express app from an external script and then want that external script to open the browser, the node callback doesn't really buy you anything.

Waiting for some magic string on stdout isn't really an improvement on just waiting for a good HTTP response. You may as well just use a try/backoff/timeout loop with <code>curl</code> until you get a successful response.

blocks|key|258991|text|您可以在服务器启动后触发自定义事件：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|258992|//+server.js
const+express+=+require('express');
const+app+=+express();

modeule.export+=+app;
app.listen(3000,+()+=>+{
+++app.emit('listened',+null)
});|code-block|syntax|javascript|258993|在一个单独的模块中，应用程序可以监听您的自定义事件：|258994|//+custom.js
const+server+=+require('server.js');
server.on('listened',+function()+{
++console.log('The+server+is+running!');
});|258995|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

You can fire a custom event after the server is started:

<pre><code>// server.js
const express = require('express');
const app = express();

modeule.export = app;
app.listen(3000, () =&gt; {
 app.emit('listened', null)
});
</code></pre>

In a separate module, the app can listen your custom event:

<pre><code>// custom.js
const server = require('server.js');
server.on('listened', function() {
 console.log('The server is running!');
});
</code></pre>

blocks|key|42151|text|server.on('listening',+function()+{
++resolve();//I+added+my+own+promise+to+help+me+await
});|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|42152|The+Listening+event为我工作。注意，我添加了我自己的承诺。我想您可以通过向此侦听器添加一个入口点来获得类似的结果，而无需承诺。|unstyled|offset|length|42153|注意，我尝试了更直观的server.on('listen')，但它不起作用。运行节点6.9.1|style|CODE|42154|entityMap|0|LINK|mutability|MUTABLE|url|https://nodejs.org/docs/latest/api/http.html#http_server_listening^0|0|0|J|0|0|B|J|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|V|8|@]|9|@$G|W|H|X|1|Y]]|A|$]]|$1|I|3|J|5|F|7|Z|8|@$G|10|H|11|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|F|7|12|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]]]

<pre><code>server.on('listening', function() {
 resolve();//I added my own promise to help me await
});
</code></pre>

<a href="https://nodejs.org/docs/latest/api/http.html#http_server_listening" rel="noreferrer">The Listening event</a> worked for me. Note I added my own Promise. I imagine you could obtain similar results without a promise by adding an entry point to this listener. 

Note, I tried the more intuitive <code>server.on('listen')</code> and it didn't work. Running node 6.9.1

blocks|key|42198|text|使用async/await语法，这可以通过将服务器启动封装在promise中来完成，因此您可以等待服务器启动，然后再运行其他任何操作：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|42199|import+express+from+'express';
import+http+from+'http';

const+app+=+express();
let+server:+http.Server;
const+startServer+=+async+():+Promise<void>+=>+{
++return+new+Promise((resolve,+_reject)+=>+{
++++server+=+app.listen(3000,+()+=>+{
++++++console.log('Express+server+started');
++++++resolve();
++++});
++});
};

await+startServer();
//+here+the+server+is+started+and+ready+to+accept+requests|code-block|syntax|javascript|42200|entityMap^0|2|B|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

With <code>async/await</code> syntax, this can be done by wrapping the server startup in a promise, so you can wait for it to be started before running anything else:
<pre><code>import express from 'express';
import http from 'http';

const app = express();
let server: http.Server;
const startServer = async (): Promise&lt;void&gt; =&gt; {
 return new Promise((resolve, _reject) =&gt; {
 server = app.listen(3000, () =&gt; {
 console.log('Express server started');
 resolve();
 });
 });
};

await startServer();
// here the server is started and ready to accept requests
</code></pre>

Have an application where I want to start a node express server and then start a browser on the same machine automatically as soon as the server is up. How can I query to see if the server is up and ready to go? I really wanted there to be some sort of callback on the .listen call, but doesn't seem to be. I could just wait a longer than I expect amount of time, but this is going on equipment that will be in the field so I either have to wait a ridiculous amount of time to make sure I'm up and running before kicking off the browser or have the user be smart enough to hit refresh if the page doesn't load right. Neither of those are good options for me. . . 

I read the API online but don't see anything like this. Surely there's a trick I don't know that can accomplish this.

If the node HTTP api (which has a callback and tells me about the listening event) is the base for the express object, maybe there is a callback option for the express call listen that isn't documented. Or perhaps I'm supposed to just know that it's there.

Any help would be greatly appreciated.

How to know when node.js express server is up and ready to use

服务器

我有一个应用程序，我想在其中启动一个node express服务器，然后一旦服务器启动，就在同一台机器上自动启动浏览器。如何查询服务器是否已启动并准备就绪？我真的希望在.listen调用上有某种回调，但似乎没有。我可以等待比我预期的时间更长的时间，但是这是在现场的设备上进行的，所以在启动浏览器之前，我必须等待一段荒谬的...

问如何了解node.js express server何时启动并可供使用
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