proxy.js

var http = require("http"),
    urlHandler = require("url");

http.createServer(function (request, response) {
    console.log(request.url);

    var options = {};
    //请求前处理
    var url = urlHandler.parse(handlerUrl(request.url));

    options.host = url.host;
    options.hostname = url.hostname;
    options.port = url.port;
    options.method = request.method;
    options.path = url.path;
    options.headers = request.headers;

    var postData = '';
    request.on("data", function(chunk){
        postData += chunk;
        console.log("post data is :" + postData);
    });

    request.on("end", function(){
        console.log("post end, data is:" + postData);

        //转发请求
        var req = http.request(options, function(res){
            console.log(res.statusCode);
            response.writeHead(res.statusCode, res.headers);
            var data = '';
            res.on("data", function(chunk){
                data += chunk;
                response.write(chunk);
            }).on("end", function(){
                //处理返回结果
                handlerResponse(url, res.statusCode, res.headers, data);
                response.end();
            }).on("error", function(e){
                console.log("problem width response: " + e.message);
            });
        });

        req.on('error', function(e) {
          console.log('problem with request: ' + e.message);
        });

        req.write(postData);
        req.end();
    });
    
    // response.end("xx");
}).listen(3128);

console.log("proxy start at 3128");

function handlerUrl(url){
    // url = url.replace(/http:\/\/mobads\.baidu\.com\/ads\/js\/exp\.js/, "http://172.17.234.116:8099/exp.js");
    if(url === 'http://mobads.baidu.com/ads/js/exp.js'){
        url = 'http://172.17.234.92:8099/exp.js';
    }
    console.log(url);
    return url;
}

function handlerResponse(url, statusCode, headers, data){
    //do something
    // console.log(url, data);
}