private void sendEnd(String index) {
        sendInstruction(new GuacamoleInstruction("end", index));
    }
Injects an "end" instruction into the outbound Guacamole protocol
stream, as if sent by the connected client. "end" instructions are used
to signal the end of a stream.

@param index
    The index of the stream that this "end" instruction relates to.
guacamole/src/main/java/org/apache/guacamole/tunnel/InputStreamInterceptingFilter.java