Remote control protocol.

Supported commands:
 f - Get frequency [Hz]
 F - Set frequency [Hz]
 m - Get demodulator mode
 M - Set demodulator mode (OFF, RAW, AM, FM, WFM, WFM_ST, WFM_ST_OIRT, LSB, USB, CW, CWL, CWU)
 l STRENGTH - Get signal strength [dBFS]
 l SQL   - Get squelch threshold [dBFS]
 L SQL <sql> - Set squelch threshold to <sql> [dBFS]
 u RECORD - Get status of audio recorder
 U RECORD <status> - Set status of audio recorder to <status>
 c - Close connection
 AOS - Acquisition of signal (AOS) event, start audio recording
 LOS - Loss of signal (LOS) event, stop audio recording
 \dump_state - Dump state (only usable for compatibility)


Reply:
 RPRT 0 - Command successful
 RPRT 1 - Command failed
