stella.ow
Class PythonClient

java.lang.Object
  util.PropertyContainer
      util.PropertyResources
          util.PropertyBundles
              io.AbstractDriver
                  stella.ow.PythonClient

All Implemented Interfaces:

Driver, Cloneable, OneWireDriver, ExitCleaning, Initializable, LocalizedSupplying, PropertySupplying, ResourceSupplying

public class PythonClient
extends AbstractDriver
implements ExitCleaning, OneWireDriver

This is a work-around to get the one-wire sensors to work. The python client talks via socket to a python server that is responible for issuing the one-wire commands. It uses a very simple ASCII-protocol that understands only three commands, LIST, READ, WRITE, or STOP.
On startup, the client connects to the server on port KEY_PYTHONPORT and keeps the connection open until closed. On init, it sends a list of readable sensors to the server. During normal operation, i.e. when sensors query the client, a read command is issued and the python server returns in plain ascii the most current value of the sensor it has in its cache. If the path issued to the python server was not sent to it previously with a list command, this method returns OneWireDriver.INVALID. Writing of the one-wire switches is accomplished in a similar way by issuing a write command to the python server. These write commands are normally not cached, but forwarded driectly to the underlying onw-wire system. The result returned is writtn by the python server to this python client. Protocol (\n means new-line):

• LIST \n\n...\n: Sends the list of sensor the python server should permanentely query. Each sensorpath has a format similar to /24.0B34086745000/temperature. This path can readily be sent to the one-wire system. It is the reponsibility of this client to send valid paths.
• READ \n: Issues a read from the cache of the python server. The last successful value read in is transferred as plain ASCII to this client. If the sensorpath queried is not in the cache list, OneWireDriver.INVALID is returned.
• WRITE \n: Write-through the requested path to the one-wire bus. The sensorpath need not to be in the cache. The result from the one-wire system, which is always an int, is converted into a plain ASCII string and sent as the response from the one-wire system.
• STOP\n: Stop the caching thread until a new list arrives. The cache is not immediately cleared, thus queries will return values still, though they might be out-of date.

Nested Class Summary

static class

PythonClient.Test A test class.

Nested classes/interfaces inherited from class util.PropertyResources

PropertyResources.URLResource

Field Summary

static String	ADD The add command string.
private static String	COMMANDSEPARATOR The separator string between multi-part commands.
private static long	DEFCOOLDOWN The default cooldown in ms.
private static String	DEFDRIVERNAME The default python driver name, a serial port name under linux
private static String	DEFPYTHONHOST The default one-wire server name, a serial port name under linux
private static int	DEFPYTHONPORT The default python server's listening port.
private static String	DEFSENSORPATH The default list of sensors.
private static long	DEFTIMEOUT The default timeout in ms.
private BufferedReader	in The input reader derived from the client socket.
static String	KEY_COOLDOWN The default time-out after writing in ms
static String	KEY_PYTHONHOST The name of the host the python server runs on.
static String	KEY_PYTHONPORT The port the python server is listening at.
static String	KEY_SENSORPATH The default list of sensor devices to read as a comma-separated list.
static String	KEY_TIMEOUT The default time-out for reading in ms
static String	LIST The list command string.
private Socket	open The client socket opened on PropertyResources.init().
private BufferedWriter	out The output writer derived from the client socket.
static String	READ The read command string.
private boolean	stalled Gets true if reading produced a time-out.
static String	STOP The stop command string.
static String	WRITE The write command string.

Fields inherited from class io.AbstractDriver

KEY_DRIVERNAME

Fields inherited from class util.PropertyBundles

KEY_LOCALECOUNTRY, KEY_LOCALELANGUAGE, KEY_RESOURCEBUNDLES

Fields inherited from class util.PropertyResources

KEY_NOINITONCREATE, localurl, locate, POSTFIX_DIR, POSTFIX_EXT, POSTFIX_FILE, POSTFIX_LIST, POSTFIX_URL, urlset

Fields inherited from class util.PropertyContainer

KEY_LISTSEPARATOR, KEY_MAPKEYVALUECHAR, KEY_MAPSEPARATOR

Fields inherited from interface stella.ow.OneWireDriver

INVALID, OK, VALID

Fields inherited from interface util.ResourceSupplying

KEY_URLRESOURCES, KEY_URLUSECONFIG, KEY_URLUSECURRENT, KEY_URLUSEHOME

Fields inherited from interface util.PropertySupplying

CONFIG, KEY_CLASS

Constructor Summary

PythonClient(Map prop)
Constructs a new python driver.

Method Summary

boolean	close() Closes the driver.
private boolean	closeSocket() Closes the socket without sending a stop to the Python server.
void	exit() On exit we close the client socket to the server and do not care about any possible failures.
boolean	isOpen() Checks if the connection is open.
int	issue(String sensorpath, String what) Sends a write command to the python server.
boolean	open() Initializes the driver.
private boolean	openSocket() Opens the socket connetion, but does not send any sensor lists.
private String	readLine() Reads a line from the input stream, and blocks if no bytes are available.
String	retrieve(String sensorpath) Send a read command to the python server.
boolean	sendList(List sensorlist) Send a list to the python server.
boolean	sendStop() Sends the stop command.
private boolean	writeLine(String what) Sends the given line to the socket's output stream.

Methods inherited from class io.AbstractDriver

createDriver, equals, getDriverName, hashCode

Methods inherited from class util.PropertyBundles

clone, getLocalized, getLocalized, getLocalizedString, getLocalizedString, loadResource

Methods inherited from class util.PropertyResources

createFrom, createFrom, createFrom, getApplet, getAsResources, getLocalClassLoader, getPropertiesToKey, getPropertiesToKey, getResource, getResourceAsStream, getResourceFromKey, getResources, init, keyCreate, keyCreate, reload, setApplet

Methods inherited from class util.PropertyContainer

augment, augment, augment, defaultBoolean, defaultChar, defaultDouble, defaultFloat, defaultInt, defaultLong, defaultObject, defaultObject, defaultProperties, defaultProperty, getAsBoolean, getAsChar, getAsDouble, getAsEnums, getAsFloat, getAsInt, getAsList, getAsLong, getAsMap, getAsMap, getAsObject, getAsObject, getProperties, getProperty, has, isNew, parseObject, reload, removeProperty, rescanned, setObject, setProperties, setProperty, stringProperties, toString

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface io.Driver

getDriverName

Methods inherited from interface util.ResourceSupplying

getResource, getResourceAsStream, getResources

Methods inherited from interface util.PropertySupplying

defaultBoolean, defaultChar, defaultDouble, defaultFloat, defaultInt, defaultLong, defaultObject, defaultObject, defaultProperties, defaultProperty, getAsBoolean, getAsChar, getAsDouble, getAsFloat, getAsInt, getAsList, getAsLong, getAsMap, getAsObject, getAsObject, getProperties, getProperty, has, parseObject, removeProperty, setObject, setProperty, stringProperties

Methods inherited from interface util.Initializable

init

Field Detail

KEY_PYTHONHOST

public static final String KEY_PYTHONHOST

The name of the host the python server runs on.

See Also:

Constant Field Values

KEY_PYTHONPORT

public static final String KEY_PYTHONPORT

The port the python server is listening at.

See Also:

Constant Field Values

KEY_SENSORPATH

public static final String KEY_SENSORPATH

The default list of sensor devices to read as a comma-separated list.

See Also:

Constant Field Values

KEY_COOLDOWN

public static final String KEY_COOLDOWN

The default time-out after writing in ms

See Also:

Constant Field Values

KEY_TIMEOUT

public static final String KEY_TIMEOUT

The default time-out for reading in ms

See Also:

Constant Field Values

DEFDRIVERNAME

private static final String DEFDRIVERNAME

The default python driver name, a serial port name under linux

See Also:

Constant Field Values

DEFPYTHONHOST

private static final String DEFPYTHONHOST

The default one-wire server name, a serial port name under linux

See Also:

Constant Field Values

DEFPYTHONPORT

private static final int DEFPYTHONPORT

The default python server's listening port.

See Also:

Constant Field Values

DEFSENSORPATH

private static final String DEFSENSORPATH

The default list of sensors.

See Also:

Constant Field Values

DEFCOOLDOWN

private static final long DEFCOOLDOWN

The default cooldown in ms.

See Also:

Constant Field Values

DEFTIMEOUT

private static final long DEFTIMEOUT

The default timeout in ms.

See Also:

Constant Field Values

LIST

public static final String LIST

The list command string.

See Also:

Constant Field Values

ADD

public static final String ADD

The add command string.

See Also:

Constant Field Values

READ

public static final String READ

The read command string.

See Also:

Constant Field Values

WRITE

public static final String WRITE

The write command string.

See Also:

Constant Field Values

STOP

public static final String STOP

The stop command string.

See Also:

Constant Field Values

COMMANDSEPARATOR

private static final String COMMANDSEPARATOR

The separator string between multi-part commands.

See Also:

Constant Field Values

open

private Socket open

The client socket opened on PropertyResources.init().

in

private BufferedReader in

The input reader derived from the client socket.

out

private BufferedWriter out

The output writer derived from the client socket.

stalled

private boolean stalled

Gets true if reading produced a time-out.

Constructor Detail

PythonClient

public PythonClient(Map prop)

Constructs a new python driver. Initially, only the sensor pathes described in the list KEY_SENSORPATH are sent to the python server.

Method Detail

open

public boolean open()
             throws IOException

Initializes the driver. This requires that the python server is up and running. On init, we open a socket connection to the python server on port KEY_PYTHONPORT. If the open is successful, we parse the initial list of sensors to query and send it to the server.

Specified by:

open in interface Driver

Returns:

True if initialization was successful.

Throws:

IOException

openSocket

private boolean openSocket()
                    throws IOException

Opens the socket connetion, but does not send any sensor lists. This method may be used on re-opening.

Throws:

IOException

closeSocket

private boolean closeSocket()
                     throws IOException

Closes the socket without sending a stop to the Python server.

Throws:

IOException

isOpen

public boolean isOpen()

Checks if the connection is open. We consider everything o.k. if we have the I/O streams and the client socket.

Specified by:

isOpen in interface Driver

Returns:

True, if a previous initialization was successful

close

public boolean close()

Closes the driver. We send a STOP to the python server and then close the socket's I/O-streams and the socket itself. If anything in this process fails, we return false. If the socket was already closed, we return true.

Specified by:

close in interface Driver

Returns:

True if clean-up was successful.

exit

public void exit()

On exit we close the client socket to the server and do not care about any possible failures.

Specified by:

exit in interface ExitCleaning

sendList

public boolean sendList(List sensorlist)

Send a list to the python server. The connection must be open for success. On receive, this list is cached for re-opening re-sends.

retrieve

public String retrieve(String sensorpath)

Send a read command to the python server. The argument must be a valid sensor path, i.e. a sensor that is in the python server's cache.

Specified by:

retrieve in interface OneWireDriver

Parameters:

sensorpath - The path to the one-wire sensor.

issue

public int issue(String sensorpath,
                 String what)

Sends a write command to the python server. The sensor path is not bound to be in the python server's cache, but it should nevertheless be a valid one. The python server's return, which is an int as a string is returned and must be interpreted from the caller's side.

Specified by:

issue in interface OneWireDriver

Parameters:

sensorpath - The path to the one-wire sensor.

what - The command to send to the one-wire sensor.

sendStop

public boolean sendStop()

Sends the stop command. This will block further updating of the cache in the python server until a new list was sent with LIST.

writeLine

private boolean writeLine(String what)

Sends the given line to the socket's output stream. The connection is NOT checked for openess, this must be ensured by the caller if desired. After each write we wait a KEY_COOLDOWN time to ensure that reading the line is possible immediately as the write returns. This is no elegant solution, but there is actually no case where we write and not read immediately afterwards.

We had mysterious dissappearance of sensor threads, which I believe is a buffer overflow in the out stream. Thus, on occasions where we're stalled, we re-open the connection, not really hoping for a cure, but trying to keep the thing alive.

Returns:

true if writing was successful.

readLine

private String readLine()

Reads a line from the input stream, and blocks if no bytes are available.