我了解如何在 Node 的新Streams2
库中使用可写流,但我不了解如何使用可读流。
dgram
以模块周围的流包装器为例:
var dgram = require('dgram');
var thumbs = {
twiddle: function() {}
};
var defaults = {
address: '0.0.0.0',
type: 'udp4',
port: 12345,
broadcast: null,
multicast: null,
multicastTTL: 1
};
var UDPStream = function(options) {
if (!(this instanceof UDPStream))
return new UDPStream(options);
Duplex.call(this);
options = options || {};
this.address = options.address || defaults.address;
this.type = options.type || defaults.type;
this.port = options.port || defaults.port;
this.broadcast = options.broadcast || defaults.broadcast;
this.multicast = options.multicast || defaults.multicast;
this.multicastTTL = options.multicastTTL || defaults.multicastTTL;
this._socket = dgram.createSocket(this.type, setup.bind(this));
this._socket.on('message', this.push.bind(this));
};
util.inherits(UDPStream, Duplex);
var setup = function() {
if (this.multicast) {
this._socket.addMembership(this.multicast);
this._socket.setMulticastTTL(this.multicastTTL);
this.destination = this.multicast;
} else {
// default to using broadcast if multicast address is not specified.
this._socket.setBroadcast(true);
// TODO: get the default broadcast address from os.networkInterfaces() (not currently returned)
this.destination = this.broadcast || '255.255.255.255';
}
};
UDPStream.prototype._read = function(size) {
thumbs.twiddle();
};
UDPStream.prototype._write = function(chunk, encoding, callback) {
this._socket.send(chunk, 0, chunk.length, this.port, this.destination);
callback();
};
module.exports = UDPStream;
除了实现之外,一切都有意义_read
。这实际上是在摆弄拇指,因为我不明白我应该在那里做什么。当 udp 套接字发出新消息时,我的数据被推送,但我无法暂停或恢复底层资源。这应该是什么样子?