RE: Confusing about DBus API specification

[Dan Williams]

On Thu, 2010-04-29 at 21:33 -0700, Nguyen Canh Toan wrote:
 Dear Dan,
 
 I do understand these fundamental concepts. Thank for your useful tutorial
 anyway.
 
 I think my problem is I do not understand object as well as interface
 hierarchy exposed by NetworkManager DBus service.
 
 According to API spec here
 (http://projects.gnome.org/NetworkManager/developers/spec-07.html#org.freede
 sktop.NetworkManager) and
 (http://live.gnome.org/NetworkManager/SystemSetting). I understand it as
 below:
 
 1. Service DBus named org.freedesktop.NetworkManagerSystemSetting and
 org.freedesktop.NetworkManagerUserSetting is one which I need to connect to
 inorder to get connection configuration.

Right, these are the service names/bus names that you need to talk to.

 2. Get org.freedesktop.NetworkManagerSettings interface of service proxy

Correct; *both* services implement this common interface, since they
provide essentially the same information.  This way you only write the
code once, and you can talk to both services easily.

 3. Invoke ListConnection() on returned interface.

I think you mean ListConnections(), but yes.

 It seems that your API spec isn't very clear so newcomers, like me, get
 confused when doing with this.

Yeah, I think what would be helpful is a general overview in the spec or
such about how the pieces fit together, possibly with a diagram and some
code examples.  I've done a bit of that and I'm about to post something
to my blog, which we can then rework into some documentation.  There are
various pages around that explain things, but mostly general overviews
and concepts and not really with code examples.  Here's one I whipped up
yesterday:

http://cgit.freedesktop.org/NetworkManager/NetworkManager/tree/examples/python/list-connections.py

There's a lot of improvement possible here, especially with examples.

 Please instruct me how to get used particularly this service. Or please make
 your spec more clearly.

I shall try.  Contributions and constructive criticism welcome, like
you've done above by pointing out that it's not clear how to talk to the
settings services.

Dan


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Re: Confusing about DBus API specification

[Pablo Martí Gamboa]

2010/4/29 Nguyen Canh Toan toan...@viettel.com.vn

  Hi all,



 After reading DBus API
 http://projects.gnome.org/NetworkManager/developers/spec-07.html#org.freedesktop.NetworkManager

 I try to list all connection setting by below interface specification

 * *

 *org.freedesktop.NetworkManagerSettings*

 The NetworkManagerSettings interface is provided by the service which
 provides connections to NetworkManager.

 Methods:

 ListConnections ( ) → ao

 List the connections stored by this Settings object.

 Returns



 connections - ao

 List of connections.



 Signals:

 NewConnection ( o: connection )

 Emitted when a new connection has been configured.

 Parameters



 connection - o

 Object path of the new connection.



 Interface has no properties.





 *Without success. *DBus service say:



 Traceback (most recent call last):

   File ./python_dbus_client, line 21, in module

 connections = manager.ListConnections()

   File /var/lib/python-support/python2.6/dbus/proxies.py, line 140, in
 __call__

 **keywords)

   File /var/lib/python-support/python2.6/dbus/connection.py, line 622, in
 call_blocking

 message, timeout)

 *dbus.exceptions.DBusException: org.freedesktop.DBus.Error.UnknownMethod:
 Method ListConnections with signature  on interface
 org.freedesktop.NetworkManager doesn't exist*


That's because ListConnections is a method of the
org.freedesktop.NetworkManagerSettings
interface ;)

Try executing your method as:

connections = manager.ListConnections(dbus_interface=
org.freedesktop.NetworkManagerSettings)

Best regards,

-- 
Pablo Martí // http://minimoesfuerzo.org
python -c print '706d617267616d40676d61696c2e636f6d'.decode('hex')
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RE: Confusing about DBus API specification

[Nguyen Canh Toan]

Thank Pablo for quickly reply, 

 

I think I am misunderstanding something. I have rewritten my script as your
advice but I still error. Here is my short script:

 

 

#!/usr/bin/env python

 

import dbus

bus = dbus.SystemBus()

 

proxy = bus.get_object(org.freedesktop.NetworkManager,
/org/freedesktop/NetworkManager)

proxy_prop = dbus.Interface(proxy, org.freedesktop.DBus.Properties)

manager = dbus.Interface(proxy, org.freedesktop.NetworkManager)

settings = dbus.Interface(proxy, org.freedesktop.NetworkManagerSettings)

 

#active connection

connections = proxy_prop.Get(org.freedesktop.NetworkManager,
ActiveConnections)

print %d % proxy_prop.Get(org.freedesktop.NetworkManager,
WirelessHardwareEnabled)

print %d % proxy_prop.Get(org.freedesktop.NetworkManager,
WirelessEnabled)

print %d % proxy_prop.Get(org.freedesktop.NetworkManager, State)

for con in connections:

print  %s % con

con_obj = bus.get_object(org.freedesktop.NetworkManager, con)

 

print list connection 

connections =
manager.ListConnections(dbus_interface=org.freedesktop.NetworkManagerSettin
gs)

for con in connections: 

print %s % con

 

 

It till say:

toa...@vt_ttpm_rd_toannc5:~/Desktop$ ./python_dbus_client 

1

1

3

 /org/freedesktop/NetworkManager/ActiveConnection/1

list connection 

Traceback (most recent call last):

  File ./python_dbus_client, line 21, in module

connections =
manager.ListConnections(dbus_interface=org.freedesktop.NetworkManagerSettin
gs)

  File /var/lib/python-support/python2.6/dbus/proxies.py, line 140, in
__call__

**keywords)

  File /var/lib/python-support/python2.6/dbus/connection.py, line 622, in
call_blocking

message, timeout)

dbus.exceptions.DBusException: org.freedesktop.DBus.Error.UnknownMethod:
Method ListConnections with signature  on interface
org.freedesktop.NetworkManagerSettings doesn't exist

 

Please help.

  _  

From: Pablo Martí Gamboa [mailto:pma...@warp.es] 
Sent: Tuesday, April 27, 2010 11:41 PM
To: Nguyen Canh Toan
Cc: networkmanager-list@gnome.org
Subject: Re: Confusing about DBus API specification

 

 

2010/4/29 Nguyen Canh Toan toan...@viettel.com.vn

Hi all, 

 

After reading DBus API
http://projects.gnome.org/NetworkManager/developers/spec-07.html#org.freedes
ktop.NetworkManager

I try to list all connection setting by below interface specification

 

org.freedesktop.NetworkManagerSettings

The NetworkManagerSettings interface is provided by the service which
provides connections to NetworkManager.

Methods:

ListConnections ( ) → ao

List the connections stored by this Settings object.

Returns

 

connections - ao

List of connections. 

 

Signals:

NewConnection ( o: connection )

Emitted when a new connection has been configured.

Parameters

 

connection - o

Object path of the new connection. 

 

Interface has no properties.

 

 

Without success. DBus service say:

 

Traceback (most recent call last):

  File ./python_dbus_client, line 21, in module

connections = manager.ListConnections()

  File /var/lib/python-support/python2.6/dbus/proxies.py, line 140, in
__call__

**keywords)

  File /var/lib/python-support/python2.6/dbus/connection.py, line 622, in
call_blocking

message, timeout)

dbus.exceptions.DBusException: org.freedesktop.DBus.Error.UnknownMethod:
Method ListConnections with signature  on interface
org.freedesktop.NetworkManager doesn't exist


That's because ListConnections is a method of the
org.freedesktop.NetworkManagerSettings interface ;)

Try executing your method as:

connections =
manager.ListConnections(dbus_interface=org.freedesktop.NetworkManagerSettin
gs)

Best regards,

-- 
Pablo Martí // http://minimoesfuerzo.org
python -c print '706d617267616d40676d61696c2e636f6d'.decode('hex')

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Re: Confusing about DBus API specification

[Jirka Klimes]

ListConnections() method is not provided by /org/freedesktop/NetworkManager 
service, rather /org/freedesktop/NetworkManagerSystemSettings and 
org.freedesktop.NetworkManagerUserSettings.
See inline comments to adapt your script.

On Thursday 29 of April 2010 11:05:13 Nguyen Canh Toan wrote:
 Thank Pablo for quickly reply,
 
 
 
 I think I am misunderstanding something. I have rewritten my script as your
 advice but I still error. Here is my short script:
 
 
 
 
 
 #!/usr/bin/env python
 
 
 
 import dbus
 
 bus = dbus.SystemBus()
 
 
 
 proxy = bus.get_object(org.freedesktop.NetworkManager,
 /org/freedesktop/NetworkManager)
 
add here
proxy1 = bus.get_object(org.freedesktop.NetworkManagerUserSettings, 
/org/freedesktop/NetworkManagerSettings)
for listing user connections or
proxy1 = bus.get_object(org.freedesktop.NetworkManagerSystemSettings, 
/org/freedesktop/NetworkManagerSettings)
for listing system-wide connections.

 proxy_prop = dbus.Interface(proxy, org.freedesktop.DBus.Properties)
 
 manager = dbus.Interface(proxy, org.freedesktop.NetworkManager)
 
 settings = dbus.Interface(proxy, org.freedesktop.NetworkManagerSettings)
You need to use proxy1 here instead of proxy.
settings = dbus.Interface(proxy1, org.freedesktop.NetworkManagerSettings)

 
 
 
 #active connection
 
 connections = proxy_prop.Get(org.freedesktop.NetworkManager,
 ActiveConnections)
 
 print %d % proxy_prop.Get(org.freedesktop.NetworkManager,
 WirelessHardwareEnabled)
 
 print %d % proxy_prop.Get(org.freedesktop.NetworkManager,
 WirelessEnabled)
 
 print %d % proxy_prop.Get(org.freedesktop.NetworkManager, State)
 
 for con in connections:
 
 print  %s % con
 
 con_obj = bus.get_object(org.freedesktop.NetworkManager, con)
 
 
 
 print list connection 
 
 connections =
 manager.ListConnections(dbus_interface=org.freedesktop.NetworkManagerSetti
 n gs)
this line should look like this:
connections = settings.ListConnections()

i.e. using settings interface and no arguments to ListConnections()

 
 for con in connections:
 
 print %s % con
 
 

Jirka
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RE: Confusing about DBus API specification

[Nguyen Canh Toan]

Dear Jirka, 

It's weird. After adjusting my script, it's still error: 

[Here is new script:]
#!/usr/bin/env python

import dbus
bus = dbus.SystemBus()

proxy = bus.get_object(org.freedesktop.NetworkManager,
/org/freedesktop/NetworkManager)
proxy_prop = dbus.Interface(proxy, org.freedesktop.DBus.Properties)
manager = dbus.Interface(proxy, org.freedesktop.NetworkManager)


#proxy_user_setting =
bus.get_object(org.freedesktop.NetworkManagerUserSettings,
/org/freedesktop/NetworkManagerUserSettings)
proxy_sys_setting =
bus.get_object(org.freedesktop.NetworkManagerSystemSettings,
/org/freedesktop/NetworkManagerSystemSettings)
settings = dbus.Interface(proxy_sys_setting,
org.freedesktop.NetworkManagerSettings)

print = active connection
connections = proxy_prop.Get(org.freedesktop.NetworkManager,
ActiveConnections)
print %d % proxy_prop.Get(org.freedesktop.NetworkManager,
WirelessHardwareEnabled)
print %d % proxy_prop.Get(org.freedesktop.NetworkManager,
WirelessEnabled)
print %d % proxy_prop.Get(org.freedesktop.NetworkManager, State)
for con in connections:
print  %s % con
con_obj = bus.get_object(org.freedesktop.NetworkManager, con)

print == list connection 
connections = settings.ListConnections()
for con in connections: 
print %s % con



[Here is log:]
toa...@vt_ttpm_rd_toannc5:~/Desktop$ ./python_dbus_client 
= active connection
1
1
3
== list connection 
Traceback (most recent call last):
  File ./python_dbus_client, line 25, in module
connections = settings.ListConnections()
  File /var/lib/python-support/python2.6/dbus/proxies.py, line 68, in
__call__
return self._proxy_method(*args, **keywords)
  File /var/lib/python-support/python2.6/dbus/proxies.py, line 140, in
__call__
**keywords)
  File /var/lib/python-support/python2.6/dbus/connection.py, line 622, in
call_blocking
message, timeout)
dbus.exceptions.DBusException: org.freedesktop.DBus.Error.UnknownMethod:
Method ListConnections with signature  on interface
org.freedesktop.NetworkManagerSettings doesn't exist


Please help.

-Original Message-
From: Jirka Klimes [mailto:jkli...@redhat.com] 
Sent: Wednesday, April 28, 2010 1:18 AM
To: networkmanager-list@gnome.org
Cc: Nguyen Canh Toan; 'Pablo Martí Gamboa'
Subject: Re: Confusing about DBus API specification

ListConnections() method is not provided by /org/freedesktop/NetworkManager 
service, rather /org/freedesktop/NetworkManagerSystemSettings and 
org.freedesktop.NetworkManagerUserSettings.
See inline comments to adapt your script.

On Thursday 29 of April 2010 11:05:13 Nguyen Canh Toan wrote:
 Thank Pablo for quickly reply,
 
 
 
 I think I am misunderstanding something. I have rewritten my script as
your
 advice but I still error. Here is my short script:
 
 
 
 
 
 #!/usr/bin/env python
 
 
 
 import dbus
 
 bus = dbus.SystemBus()
 
 
 
 proxy = bus.get_object(org.freedesktop.NetworkManager,
 /org/freedesktop/NetworkManager)
 
add here
proxy1 = bus.get_object(org.freedesktop.NetworkManagerUserSettings, 
/org/freedesktop/NetworkManagerSettings)
for listing user connections or
proxy1 = bus.get_object(org.freedesktop.NetworkManagerSystemSettings, 
/org/freedesktop/NetworkManagerSettings)
for listing system-wide connections.

 proxy_prop = dbus.Interface(proxy, org.freedesktop.DBus.Properties)
 
 manager = dbus.Interface(proxy, org.freedesktop.NetworkManager)
 
 settings = dbus.Interface(proxy, org.freedesktop.NetworkManagerSettings)
You need to use proxy1 here instead of proxy.
settings = dbus.Interface(proxy1, org.freedesktop.NetworkManagerSettings)

 
 
 
 #active connection
 
 connections = proxy_prop.Get(org.freedesktop.NetworkManager,
 ActiveConnections)
 
 print %d % proxy_prop.Get(org.freedesktop.NetworkManager,
 WirelessHardwareEnabled)
 
 print %d % proxy_prop.Get(org.freedesktop.NetworkManager,
 WirelessEnabled)
 
 print %d % proxy_prop.Get(org.freedesktop.NetworkManager, State)
 
 for con in connections:
 
 print  %s % con
 
 con_obj = bus.get_object(org.freedesktop.NetworkManager,
con)
 
 
 
 print list connection 
 
 connections =

manager.ListConnections(dbus_interface=org.freedesktop.NetworkManagerSetti
 n gs)
this line should look like this:
connections = settings.ListConnections()

i.e. using settings interface and no arguments to ListConnections()

 
 for con in connections:
 
 print %s % con
 
 

Jirka

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RE: Confusing about DBus API specification

[Dan Williams]

On Thu, 2010-04-29 at 06:08 -0700, Nguyen Canh Toan wrote:
 Dear Jirka, 
 
 It's weird. After adjusting my script, it's still error: 

D-Bus is simply an IPC mechanism, but it layers a few concepts on top of
pure message-passing, as explained below.  It did take me some time to
understand how the D-Bus object model really works, so don't worry about
it you don't completely understand how it all works yet.

1) 'service': a program that responds to requests from clients.  Each
service is identified by a bus name which clients use to find the
service and send requests to it.  The bus name usually looks like
org.foobar.Baz.  A program can claim more than one bus name; NM claims
org.freedesktop.NetworkManager and
org.freedesktop.NetworkManagerSystemSettings, each is a unique serivce
which provides different functionality to clients.

2) 'object': a method of organizing distinct entities, much like
programming languages have objects.  Each object is uniquely identified
by an object path (basically a pointer) that looks like
/org/foobar/Baz/235235. Each request sent to the service must be
directed to a specific object.  Many services have a base object with a
well-known path that you use to bootstrap your communication with the
service.

3) 'interface': each request belongs to an interface, which is simply a
way of logically separating different functionality.  The same way that
object-oriented languages like Java or C++ or GLib define an
interface; a specific API that different objects can implement, but
the caller doesn't need to know what type the object is, just the
interface.  Interface names often look like D-Bus service names, but
have no relation to them.

4) 'method call': a request for an operation or information that a
client sends to the service; method calls are defined by an Interface
and are sent to objects.

Say you have a binary called mcdonaldsd that provides a D-Bus service
called org.fastfood.McDonalds.  Clients that want to talk to this
service use org.fastfood.McDonalds to direct requests to mcdonaldsd.

mcdonaldsd provides a base object called /org/fastfood/McDonalds.
This object implements the org.fastfood.McDonalds interface, which
defines the method calls:

  - GetItems(void) - ao
  - Order(ao) - b

GetItems returns an array of object-paths representing all the things on
the menu that you can order.  So if you call it you'll get something
like this returned:

[ '/org/fastfood/McDonalds/Item/0', '/org/fastfood/McDonalds/Item/1' ]

Each of these returned object paths is a pointer to an object;
mcdonaldsd probably even implements these as objects internally using
Java or C++ or GObject or whatever.  These objects are probably
completely different (one may be a burger, one may be a drink) but they
all implement a common interface org.fastfood.McDonalds.Item.

The org.fastfood.McDonalds.Item interface has the following method
calls:

  - GetName
  - GetType  (either TYPE_BURGER, TYPE_DRINK, or TYPE_FRIES)
  - GetPrice
  - Consume

So even if you don't know what /org/fastfood/McDonalds/Item/0 is, you
still can get a lot of information about it, enough to decide whether
you want to order it or not.

Assume that item 0 is a BigMac and item 1 is Coke.  These are
clearly different objects, but each still has a name, a calorie count, a
price, and can be consumed.

Next, since each item is different (even though they all implement the
common org.fastfood.McDonalds.Item interface) each item type will
implement other interfaces that define functionality specific to that
type of item.

So item 0 (BigMac) implements the org.fastfood.McDonalds.Item.Burger
interface which has the following methods:

  - Unwrap
  - AddMustard
  - RemovePickle (nobody likes those stupid limp pickles anyway)

And item 1 (Coke) implements the org.fastfood.McDonalds.Item.Drink
interface which has the following methods:

  - PutLidOn
  - InsertStraw
  - RemoveStraw

Remember, since both objects *also* implement the base
org.fastfood.McDonalds.Item interface, you can use the Consume() method
to consume both items.  But clearly, you don't want to include the
InsertStraw() method on the generic org.fastfood.McDonalds.Item
interface, because all items implement that interface, and it would be
pretty funny if you tried to call InsertStraw() on the BigMac object.
People would stare.

So interfaces are about logically separating method calls that have
specific functionality, and thus any object that wants that
functionality can implement that interface, instead of having every
object type duplicate all the calls of that interface.

So, with pseudocode:

# Get local proxy for the remove mcdonaldsd service
bus = get_service(org.fastfood.McDonalds)
mcds = bus.get_object(org.fastfood.McDonalds, /org/fastfood/McDonalds)

burger_path = None
drink_path = None

# Lets read all the menu items
menu_items = mcds.GetItems()
for object_path in menu_items:
item = bus.get_object(org.fastfood.McDonalds.Item, object_path)
print Item: %s price 

RE: Confusing about DBus API specification

[Nguyen Canh Toan]

Dear Dan,

I do understand these fundamental concepts. Thank for your useful tutorial
anyway.

I think my problem is I do not understand object as well as interface
hierarchy exposed by NetworkManager DBus service.

According to API spec here
(http://projects.gnome.org/NetworkManager/developers/spec-07.html#org.freede
sktop.NetworkManager) and
(http://live.gnome.org/NetworkManager/SystemSetting). I understand it as
below:

1. Service DBus named org.freedesktop.NetworkManagerSystemSetting and
org.freedesktop.NetworkManagerUserSetting is one which I need to connect to
inorder to get connection configuration.
2. Get org.freedesktop.NetworkManagerSettings interface of service proxy
3. Invoke ListConnection() on returned interface.


It seems that your API spec isn't very clear so newcomers, like me, get
confused when doing with this.

Please instruct me how to get used particularly this service. Or please make
your spec more clearly.

Thank for your time  consideration.
Toan Nguyen 

-Original Message-
From: Dan Williams [mailto:d...@redhat.com] 
Sent: Wednesday, April 28, 2010 11:52 AM
To: Nguyen Canh Toan
Cc: jkli...@redhat.com; networkmanager-list@gnome.org
Subject: RE: Confusing about DBus API speciDan Williams
[d...@redhat.com]fication

On Thu, 2010-04-29 at 06:08 -0700, Nguyen Canh Toan wrote:
 Dear Jirka, 
 
 It's weird. After adjusting my script, it's still error: 

D-Bus is simply an IPC mechanism, but it layers a few concepts on top of
pure message-passing, as explained below.  It did take me some time to
understand how the D-Bus object model really works, so don't worry about
it you don't completely understand how it all works yet.

1) 'service': a program that responds to requests from clients.  Each
service is identified by a bus name which clients use to find the
service and send requests to it.  The bus name usually looks like
org.foobar.Baz.  A program can claim more than one bus name; NM claims
org.freedesktop.NetworkManager and
org.freedesktop.NetworkManagerSystemSettings, each is a unique serivce
which provides different functionality to clients.

2) 'object': a method of organizing distinct entities, much like
programming languages have objects.  Each object is uniquely identified
by an object path (basically a pointer) that looks like
/org/foobar/Baz/235235. Each request sent to the service must be
directed to a specific object.  Many services have a base object with a
well-known path that you use to bootstrap your communication with the
service.

3) 'interface': each request belongs to an interface, which is simply a
way of logically separating different functionality.  The same way that
object-oriented languages like Java or C++ or GLib define an
interface; a specific API that different objects can implement, but
the caller doesn't need to know what type the object is, just the
interface.  Interface names often look like D-Bus service names, but
have no relation to them.

4) 'method call': a request for an operation or information that a
client sends to the service; method calls are defined by an Interface
and are sent to objects.

Say you have a binary called mcdonaldsd that provides a D-Bus service
called org.fastfood.McDonalds.  Clients that want to talk to this
service use org.fastfood.McDonalds to direct requests to mcdonaldsd.

mcdonaldsd provides a base object called /org/fastfood/McDonalds.
This object implements the org.fastfood.McDonalds interface, which
defines the method calls:

  - GetItems(void) - ao
  - Order(ao) - b

GetItems returns an array of object-paths representing all the things on
the menu that you can order.  So if you call it you'll get something
like this returned:

[ '/org/fastfood/McDonalds/Item/0', '/org/fastfood/McDonalds/Item/1' ]

Each of these returned object paths is a pointer to an object;
mcdonaldsd probably even implements these as objects internally using
Java or C++ or GObject or whatever.  These objects are probably
completely different (one may be a burger, one may be a drink) but they
all implement a common interface org.fastfood.McDonalds.Item.

The org.fastfood.McDonalds.Item interface has the following method
calls:

  - GetName
  - GetType  (either TYPE_BURGER, TYPE_DRINK, or TYPE_FRIES)
  - GetPrice
  - Consume

So even if you don't know what /org/fastfood/McDonalds/Item/0 is, you
still can get a lot of information about it, enough to decide whether
you want to order it or not.

Assume that item 0 is a BigMac and item 1 is Coke.  These are
clearly different objects, but each still has a name, a calorie count, a
price, and can be consumed.

Next, since each item is different (even though they all implement the
common org.fastfood.McDonalds.Item interface) each item type will
implement other interfaces that define functionality specific to that
type of item.

So item 0 (BigMac) implements the org.fastfood.McDonalds.Item.Burger
interface which has the following methods:

  - Unwrap
  - AddMustard
  - RemovePickle (nobody likes those