Processing POST using Forms

Limiting the length of POST data to prevent filling memory?

A POST from a client sends a header and a block of data. If a client sends too much data at once the server will run out of space and crash. I added code to ignore POST data over a certain size.
Is this sufficient or should an req.on('data) be used to drain the buffer at the req source?

function serveHTML(){
var http=require("http").createServer(onPageRequest).listen(8080);
}//end serveFile

var pdata="";
function onPageRequest(req, res) { 
//console.log("Req= ",req);
//console.log("Header",req.headers);
if (req.method=="POST") {
  console.log("Post");
  doPost(req,res);
}else{
  doGet(req,res);
}//endif
}//end on PageRequest

var pobj;


function doPost(req,res){
var length;
  length=req.headers["Content-Length"];
//do we want to take the message based on length?
  if(length<1024){
  req.on("data", function(d) {pdata+=d;if(pdata.length==length)doPost1(req,res);});
  }else{
/*********
Should an req.on('data') be used here to drain the source and toss the data?
*/

  res.writeHead(413); //Too big error
  res.end();  }//end if length    
  req.on('close',"console.log(\"Closed\",pdata);");
}

The POST message processing code follows.

function doPost1(req,res){
var length;
var a = url.parse(req.url, true);
console.log("URL ",a);
console.log("XXX ",a.pathname);
  length=req.headers["Content-Length"];
  console.log("Length ",length);
  console.log("pdata= ",pdata);
  console.log("pdata length= ",pdata.length);
  switch (a.pathname){
    case "/CMD":                                //Process JSON command structure
     if(pdata.length==length){
      pobj=JSON.parse(pdata);
      console.log(pobj);
      if(pobj.cmd !==null){
       eval(pobj.cmd);
       pdata=JSON.stringify(pobj);
       res.writeHead(200);
       res.end(pdata);
      }else{
       res.writeHead(201);
       res.end();
      }  //end if pobj.cmd
     }//endif length else
    break;
    case "/LOGdata":    // Process data POSTed into a form, simple Echo for now
     console.log("LOGdata= ",pdata);
     res.writeHead(200);
     res.end(pdata);
    break;
    default:
     res.writeHead(404);
     res.end();
 }//end switch
 pdata="";
}//end doPost1