Error while publishing encoder ticks in Arduino

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I am using Arduino Uno to publish Rotary Encoder ticks. I have used the following code to publish the encoder values to ROS and ended up in the error

#include <ros.h>
#include <std_msgs/Int16.h>
#include <std_msgs/Int32.h>
#include <std_msgs/Int64.h>
#include <std_msgs/Float32.h>

int val;
 int encoder0PinA = 2;
 int encoder0PinB = 3;
 int encoder0PinZ = 4;
 int lwheel = 0;
 int encoder0PinALast = LOW;
 int n = LOW;

ros::NodeHandle  nh;

std_msgs::Int16 lwheelMsg;
ros::Publisher lwheelPub("lwheel", &lwheelMsg);   /

 void setup() {
   Serial.begin(57600);  
   pinMode (encoder0PinA,INPUT);
   pinMode (encoder0PinB,INPUT);
  nh.initNode();
  nh.advertise(lwheelPub);

 }

void loop() {

   n = digitalRead(encoder0PinA);
   if ((encoder0PinALast == LOW) && (n == HIGH)) {
     if (digitalRead(encoder0PinB) == LOW) {
       lwheel--;
     } else {
       lwheel++;
     }
     Serial.print (lwheel*0.97);
     Serial.print ("mm/");
lwheelPub.publish(&lwheelMsg);
   }
   encoder0PinALast = n;
nh.spinOnce();
 }

ERROR

[WARN] [WallTime: 1473618880.299270] Serial Port read returned short (expected 2 bytes, received 1 instead).
[WARN] [WallTime: 1473618880.300057] Serial Port read failure:

I found some fixes which told to change the baud rate, i tried them but didn't help. Someone please help me to fix the issue and direct me to correct ROS Arduino node to publish encoder ticks to ROS with interupt.