Getting 16 bytes at a time from .txt

I Have two files one sending, one receiving. I have the connection between the two.

can send text with :

// Prepare a message 
 messageToSend = "text that is sent";
 lengthMessageToSend = messageToSend.length(); 
 sendingBuffer = messageToSend.getBytes();


// Send the message
 myLink.sendFrame(sendingBuffer, lengthMessageToSend);
 System.out.println(lengthMessageToSend);

And Receive with :

// Display the message
  messageReceived = new String(receivingBuffer, 0, lengthMessageReceived);
  System.out.println("Message received is: [" + messageReceived + "]"); 

// Prepare a message  
  messageToSend = "1";
  lengthMessageToSend = messageToSend.length(); 
  sendingBuffer = messageToSend.getBytes();

 // Send the message
  myLink.sendFrame(sendingBuffer, lengthMessageToSend);

The text I am trying to now send is from a .txt, but just to send 16 bytes at a time within a payload:

[ SEQ | LEN | PAYLOAD | CHECKSUM ] --> for a total Header of 19 bytes.

What would the best way of doing this ?

Just reading in 16 bytes(8 characters) at a time?? If so How?