javascript - 传递刚刚创建的参数

Question

我正在创建一个 NodeJS/Express 监听器，并在创建 connectListener 时创建输入:

app.get('/server/:args', function(req, res) {
   res.sendFile(__dirname + '/index.html');
   // ... 
   var args = req.param("args");
   var client = net.connect({port : 50505}, connectListener(args, client));
});

然后我就有了 connectListener 函数:

function connectListener(args, client) {
    console.log("Connected to server.");
    console.log(args);
    client.write(args);
    // .... 
}

但是，我收到参数未定义的错误:

TypeError: Cannot read property 'write' of undefined
    at connectListener (C:\Users\ES\workspace_luna\WptHash\server-src\index.js:39:8)
    at C:\Users\ES\workspace_luna\WptHash\server-src\index.js:33:43
    at Layer.handle [as handle_request] (C:\Users\ES\workspace_luna\WptHash\server-src\node_modules\express\lib\router\layer.js:82:5)
    at next (C:\Users\ES\workspace_luna\WptHash\server-src\node_modules\express\lib\router\route.js:100:13)
    at Route.dispatch (C:\Users\ES\workspace_luna\WptHash\server-src\node_modules\express\lib\router\route.js:81:3)
    at Layer.handle [as handle_request] (C:\Users\ES\workspace_luna\WptHash\server-src\node_modules\express\lib\router\layer.js:82:5)
    at C:\Users\ES\workspace_luna\WptHash\server-src\node_modules\express\lib\router\index.js:235:24
    at param (C:\Users\ES\workspace_luna\WptHash\server-src\node_modules\express\lib\router\index.js:332:14)
    at param (C:\Users\ES\workspace_luna\WptHash\server-src\node_modules\express\lib\router\index.js:348:14)
    at Function.proto.process_params (C:\Users\ES\workspace_luna\WptHash\server-src\node_modules\express\lib\router\index.js:392:3)
Error: Can't set headers after they are sent.
    at SendStream.headersAlreadySent (C:\Users\ES\workspace_luna\WptHash\server-src\node_modules\express\node_modules\send\index.js:313:13)
    at SendStream.send (C:\Users\ES\workspace_luna\WptHash\server-src\node_modules\express\node_modules\send\index.js:494:17)
    at onstat (C:\Users\ES\workspace_luna\WptHash\server-src\node_modules\express\node_modules\send\index.js:585:10)
    at FSReqWrap.oncomplete (fs.js:99:15)

那么，如何正确创建 client 变量以便在下面的函数中使用它？我制作这样的函数 connectListener 而不是内联的原因是我计划跨更多端口复制客户端以处理同时连接，因此我不想重复使用代码，也不想使用一组全局客户端变量/数组(尽管我想我可以......)

Answer 1

看起来问题是您正在调用 connectListener ，您应该将其设置为在连接事件上调用的函数:

var client = net.connect({port : 50505}, connectListener);

如果您想使用特定参数写入特定客户端，可以通过在 connectListener 函数中定义响应来实现:

app.get('/server/:args', function (req, res) {
    var client, args;

    res.sendFile(__dirname + '/index.html');
    // ... 

   function connectListener () {
       console.log("Connected to server.");
       console.log(args);
       client.write(args);
       // .... 
   }

   args = req.param("args");
   client = net.connect({port : 50505}, connectListener);
});