Writing image data from android app to node js server

I am trying to upload file from android app and want to write that data to our server(saving file to our server) I am able to write to a file but that image won't display

My code of snippet:-

var data='';
          req.setEncoding('binary'); // also try UTF8
          req.on('data', function(chunk) {
             data += chunk;
            // f.write(chunk);
          });
          req.on('end', function() {
              let fileData = {};
              fileData.filename = filename;
              fileData.fileextension = fileextension;
               fs.writeFile(completeFilename, data, 'binary', function (err) {
                  if(err){
                    console.log(err);
                    let response_data = status_codes.file_uplpoad_error;
                    console.log(response_data);
                    let enc   = encrypt_decrypt.encrypt(cryptkey, iv, JSON.stringify(response_data));
                    res.end(enc);
                  }else{
                    let fileData = {};
                    fileData.filename = filename;
                    fileData.fileextension = fileextension; 
                    return callback(fileData);
                  }
              });


});
req.on('error', function(err) {
            // This prints the error message and stack trace to `stderr`.
            console.error(err.stack);
            console.log(err);
            res.end('error');
          });

Where I am getting wrong unable to know as everything worked wellexcept writing of image

Tried all things but unable to get it done Thanks in advance :)

via VIKAS KOHLI