@Override
    public char[] read() throws GuacamoleException {
        GuacamoleInstruction instruction = readInstruction();
        if (instruction == null)
            return null;

        return instruction.toCharArray();
    }
The number of characters currently used within the data buffer. All
other characters within the buffer are free space available for
future reads.
guacamole-common/src/main/java/org/apache/guacamole/io/ReaderGuacamoleReader.java