function proxyTDTMapData(img,level,row,col){ 
 var that = this,request = null,param = img.replace('_w',''); 
 var filename = tdtimgDir+'/'+img+'_'+level+'_'+row+'_'+col+'.png'; 
 path.exists(filename, function(exists) { 
 if (exists) { 
 readFileEntry(filename,that.res); 
 }else{ 
 var url = "http://t0.tianditu.com/"+img+"/wmts?service=wmts&request=GetTile&version=1.0.0&LAYER=" + param + "&tileMatrixSet=w&TileRow=" + row + "&TileCol=" + col + "&TileMatrix=" + level + "&style=default&format=tiles"; 
 
 httpGetWithTimeoutSupport(url,4000,function(response){ 
 //console.log("have a response!"); 
 if(200 == response.statusCode){ 
 var size = 0; 
 var chunks = []; 
 response.on('data', function(chunk){ 
 size += chunk.length; 
 chunks.push(chunk); 
 }); 
 response.on('end', function(){ 
 var data = Buffer.concat(chunks, size); 
 that.res.writeHead(200, { 
 'Content-Type' : 'image/png', 
 'Content-Length' : data.length, 
 'Accept-Ranges' : 'bytes', 
 'Server' : 'Microsoft-IIS/7.5', 
 'X-Powered-By' : 'ASP.NET' 
 }); 
 that.res.write(data, "binary"); 
 that.res.end(); 
 fs.writeFile(tdtimgDir+'/'+img+'_'+level+'_'+row+'_'+col+'.png', data); 
 }); 
 }else{ 
 readFileEntry(mapDir+"/null.png",that.res); 
 } 
 }).on("error",function(){ 
 readFileEntry(mapDir+"/null.png",that.res); 
 }); 
 } 
 }); 
 
 
 } 

function httpGetWithTimeoutSupport(options, timeout, callback) { 
 var timeoutEvent; 
 
 var req = http.get(options, function(res) { 
 res.on("end", function() { 
 clearTimeout(timeoutEvent); 
 // console.log("end"); 
 }) 
 res.on("close", function(e) { 
 clearTimeout(timeoutEvent); 
 // console.log("close"); 
 }) 
 
 res.on("abort", function() { 
 // console.log("abort"); 
 }); 
 
 res.on("error",function(){ 
 try{ 
 res.destory(); 
 clearTimeout(timeoutEvent); 
 //console.log("res error catch"); 
 }catch(e){ 
 
 } 
 }); 
 callback(res); 
 }); 
 
 req.on("timeout", function() { 
 //console.log("request emit timeout received"); 
 try{ 
 if (req.res) { 
 req.res.emit("abort"); 
 } 
 clearTimeout(timeoutEvent); 
 req.abort(); 
 }catch(e){ 
 //console.log("req timeout failed!"); 
 } 
 }); 
 req.on("error",function(){ 
 try{ 
 //console.log("req error catch"); 
 }catch(e){ 
 
 } 
 }); 
 timeoutEvent = setTimeout(function() { 
 try{ 
 req.emit("timeout"); 
 }catch(e){ 
 //console.log("timeout failed!"); 
 } 
 }, timeout); 
 
 return req; 
} 

path.exists(filename, function(exists) { 
 if (exists) { 
 readFileEntry(filename,that.res); 
 }else{...});