agent.createConnection(options[, callback])

• options <Object> 包含连接详细信息的选项。 查看 net.createConnection() 以获取选项的格式
• callback <Function> 接收创建的套接字的回调函数
• 返回: <stream.Duplex>

生成用于 HTTP 请求的套接字/流。

默认情况下，此函数与 net.createConnection() 相同。 但是，如果需要更大的灵活性，自定义代理可能会覆盖此方法。

可以通过以下两种方式之一提供套接字/流：通过从此函数返回套接字/流，或将套接字/流传给 callback。

此方法保证返回 <net.Socket> 类（<stream.Duplex> 的子类）的实例，除非用户指定 <net.Socket> 以外的套接字类型。

callback 的参数为 (err, stream)。

• options <Object> Options containing connection details. Check net.createConnection() for the format of the options
• callback <Function> Callback function that receives the created socket
• Returns: <stream.Duplex>

Produces a socket/stream to be used for HTTP requests.

By default, this function is the same as net.createConnection(). However, custom agents may override this method in case greater flexibility is desired.

A socket/stream can be supplied in one of two ways: by returning the socket/stream from this function, or by passing the socket/stream to callback.

This method is guaranteed to return an instance of the <net.Socket> class, a subclass of <stream.Duplex>, unless the user specifies a socket type other than <net.Socket>.

callback has a signature of (err, stream).