我试图了解node.js中addListener的用途.有人可以解释一下吗？一个简单的例子是:vartcp=require('tcp');varserver=tcp.createServer(function(socket){socket.setEncoding("utf8");socket.addListener("connect",function(){socket.write("hello\r\n");});socket.addListener("data",function(data){socket.write(data);});socket.addListener("end"