PHD Socket Server Interface

PHD supports control and monitoring through its Socket Server interface.

Note: using the socket server for status monitoring has been superseded by the EventMonitoring interface which provides much more detailed status information.

When the server is enabled (Tools -> Enable Server), PHD2 listens for TCP connections on port 4300. It accepts one-byte commands and sends one-byte responses. PHD2 supports multiple concurrent client connections. When there are multiple PHD2 instances, each instance listens on successive TCP port numbers (4301, 4302, ...).

The available commands are given in the table below. The command and response are each a single byte with the indicated values.

Command name	Value	Description	Response
MSG_PAUSE	1	Pause guiding. Camera exposures continue to loop if they are already looping.	0
MSG_RESUME	2	Resume guiding if it was paused, otherwise no effect.	0
MSG_MOVE1	3	Dither a random amount, up to +/- 0.5 x dither_scale	Camera exposure time in seconds, but not less than 1
MSG_MOVE2	4	Dither a random amount, up to +/- 1.0 x dither_scale	Camera exposure time in seconds, but not less than 1
MSG_MOVE3	5	Dither a random amount, up to +/- 2.0 x dither_scale	Camera exposure time in seconds, but not less than 1
MSG_IMAGE	6	(not currently implemented in PHD2)	1
MSG_GUIDE	7	(not currently implemented in PHD2)	1
MSG_CAMCONNECT	8	(not currently implemented in PHD2)	1
MSG_CAMDISCONNECT	9	(not currently implemented in PHD2)	1
MSG_REQDIST	10	Request guide error distance	The current guide error distance in units of 1/100 pixel. Values > 255 are reported as 255.
MSG_REQFRAME	11	(not currently implemented in PHD2)	1
MSG_MOVE4	12	Dither a random amount, up to +/- 3.0 x dither_scale	Camera exposure time in seconds, but not less than 1
MSG_MOVE5	13	Dither a random amount, up to +/- 5.0 x dither_scale	Camera exposure time in seconds, but not less than 1
MSG_AUTOFINDSTAR	14	Auto-select a guide star.	1 if a star was selected, 0 if not
MSG_SETLOCKPOSITION	15	Read 2 16-bit integers, x and y,from the socket and set the lock position to (x,y)	0
MSG_FLIPRACAL	16	Flip RA calibration data	1 if RA calibration data was flipped, 0 otherwise
MSG_GETSTATUS	17	Get a value describing the state of PHD	0: not paused, looping, or guiding 1: capture active and star selected 2: calibrating 3: guiding and locked on star 4: guiding but star lost 100: paused 101: looping but no star selected
MSG_STOP	18	Stop looping exposures or guiding	0. Client should poll with MSG_GETSTATUS to check that looping/guiding has actually stopped.
MSG_LOOP	19	Start looping exposures	0 if request to start looping was accepted, non-zero otherwise (like when looping was already active). Client should poll with MSG_GETSTATUS to see if looping actually started.
MSG_STARTGUIDING	20	Start guiding	0. Client should poll with MSG_GETSTATUS to check that guiding has actually started.
MSG_LOOPFRAMECOUNT	21	Get the current frame counter value.	0 if not looping or guiding. Otherwise, the current frame counter value (capped at 255). The frame counter is incremented for each camera exposure when looping or guiding.
MSG_CLEARCAL	22	Clear calibration data (force re-calibration)	0
MSG_FLIP_SIM_CAMERA	23	When the camera simulator is active, simulate a scope meridian flip	0
MSG_DESELECT	24	De-select the currently selected guide star. If subframes are enabled, switch to full frames. This command should be sent before sending MSG_AUTOFINDSTAR to ensure a full frame is captured. For example, the following sequence could be used to select a guide star: MSG_STOP, MSG_DESELECT, MSG_LOOP, MSG_LOOPFRAMECOUNT, MSG_AUTOFINDSTAR.	0
		unknown command	1