新手求问一个事件监听问题

问一个问题 Node入门 里面有个例子，处理POST请求的时候 可以注册监听器 request.addListener("data", function(chunk) { // called when a new chunk of data was received });

request.addListener("end", function() { // called when all chunks of data have been received });

data事件代表post数据来到 end事件代表数据接收完

但是在程序里怎么知道什么时候出发data事件，什么时候触发end事件呢 代码是 var http = require("http"); var url = require("url");

function start(route, handle) { function onRequest(request, response) { var postData = ""; var pathname = url.parse(request.url).pathname; console.log("Request for " + pathname + " received.");

request.setEncoding("utf8");

request.addListener("data", function(postDataChunk) {
  postData += postDataChunk;
  console.log("Received POST data chunk '"+
  postDataChunk + "'.");
});

request.addListener("end", function() {
  route(handle, pathname, response, postData);
});

}

http.createServer(onRequest).listen(8888); console.log("Server has started."); }

exports.start = start; 难道data和end事件本来就存在？注册了就能用？否则以上面代码看，怎么知道什么时候触发data和end？ 如果不是，那事件名字可以随便取吗？