How to convert signed 16 bit integer to unsigned 16 bit integer in Java?

I have my below layout in which I need to represent my data and then finally I need to make one byte array out of that. I need to represent my data in the below format from Java code and then send the byte array to my C++ program which in turns c++ program unpacks the byte array and extract the relevant stuff from it -

// below is my data layout -
//
// key type - 1 byte
// key len - 1 byte
// key (variable size = key_len)
// timestamp (sizeof uint64_t)
// data size (sizeof uint16_t), this is unsigned 16-bit integer.
// data (variable size = data size)

So I started like this in Java which works fine on a simple use case which makes a single byte array out of this but I am thinking my dataSize calculation is wrong since I am using Short for the dataSize which can take maximum value as 32767 but dataSize specification is uint16_t as shown above which is unsigned 16-bit integer which can take maximum value more than 32767.

byte keyType = 101;
byte keyLength = 3;
byte[] key = {27, 55, 111};
long timestamp = System.currentTimeMillis();

byte[] data = "string data".getBytes("UTF-8");

// this is looking wrong to me since dataSize is uint16_t in my C++ specifications as shown above
short dataSize = (short) data.length;

int totalSize = (1 + 1 + keyLength + 8 + 2 + dataSize);
ByteBuffer bytes = ByteBuffer.allocate(totalSize);

bytes.put(keyType);
bytes.put(keyLength);
bytes.put(key);
bytes.putLong(timestamp);

// so this is also wrong
// what is the right way to send the dataSize?
bytes.putShort(dataSize);
bytes.put(data);

// write everthing as a single byte array:
byte[] byteArray = bytes.array();

Let's say if the length of data is 37714 (data.length), then dataSize will come as negative -27822.

So my question is - Is there any way I can have unsigned 16 bit Integer in java which I can use in my above code or some way to cast it?