Python DBus 未知方法或接口

问题描述 投票：0回答：1

我正在遵循here找到的 Linux 蓝牙开发学习指南，并且是 DBus 编程的新手。

本指南使用 Python 与系统 DBus 进行交互，如下所示。

#!/usr/bin/python3
import dbus

bus = dbus.SystemBus()
proxy = bus.get_object('org.freedesktop.hostname1','/org/freedesktop/hostname1')
interface = dbus.Interface(proxy, 'org.freedesktop.Dbus.Properties')

print("----------------")
hostname = interface.Get('org.freedesktop.hostname1','Hostname')
print("The host name is ",hostname)

但是，当调用interface.Get方法时，出现以下错误。

dbus.exceptions.DBusException: org.freedesktop.DBus.Error.UnknownMethod: Unknown method Get or interface org.freedesktop.Dbus.Properties.

我可以使用 d-feet 运行 org.freedesktop.hostname1 对象的 org.freedesktop.Dbus.Properties 接口的 Get 方法，该方法按预期返回主机名。我也尝试过以 root 身份运行 python 脚本，但仍然遇到相同的错误。

我使用 dbus-monitor 对 Wireshark 进行了 pcap 捕获，并将 d-feet 请求与 python dbus 请求进行了比较，我无法看出问题所在。两个请求都发送到相同的目的地，并且看起来结构相同，具有相同的相关细节，除了字典元素数组似乎具有不同的顺序（不确定这是否重要）。

d 脚要求：

Frame 17: 197 bytes on wire (1576 bits), 197 bytes captured (1576 bits)
    Encapsulation type: D-Bus (146)
    Arrival Time: Mar 13, 2024 07:21:04.048618000 AEDT
    [Time shift for this packet: 0.000000000 seconds]
    Epoch Time: 1710274864.048618000 seconds
    [Time delta from previous captured frame: 0.001328000 seconds]
    [Time delta from previous displayed frame: 0.001328000 seconds]
    [Time since reference or first frame: 2.546796000 seconds]
    Frame Number: 17
    Frame Length: 197 bytes (1576 bits)
    Capture Length: 197 bytes (1576 bits)
    [Frame is marked: False]
    [Frame is ignored: False]
    [Protocols in frame: dbus]
D-Bus
    Endianness: little-endian
    Message Type: Method call
    Message Flags: 0x00
        .... ...0 = No Reply Expected: Expected
        .... ..0. = No Auto Start: Start
        .... .0.. = Allow Interactive Authorization: Don't allow
    Protocol Version: 1
    Message Body Length: 45
    Message Serial: 623
    Header Field Array
        Array Length: 134
        Dict Entry, 1, Path: /org/freedesktop/hostname1
            Field Code: Path (1)
            Variant: /org/freedesktop/hostname1
                Variant Signature: o
                Path: /org/freedesktop/hostname1
        Dict Entry, 2, Interface: org.freedesktop.DBus.Properties
            Field Code: Interface (2)
            Variant: org.freedesktop.DBus.Properties
                Variant Signature: s
                Interface: org.freedesktop.DBus.Properties
        Dict Entry, 6, Destination: :1.171
            Field Code: Destination (6)
            Variant: :1.171
                Variant Signature: s
                Destination: :1.171
        Dict Entry, 8, Signature: ss
            Field Code: Signature (8)
            Variant: ss
                Variant Signature: g
                Signature: ss
        Dict Entry, 3, Member: Get
            Field Code: Member (3)
            Variant: Get
                Variant Signature: s
                Member: Get
        Dict Entry, 7, Sender: :1.83
            Field Code: Sender (7)
            Variant: :1.83
                Variant Signature: s
                Sender: :1.83
    Body
        String: org.freedesktop.hostname1
        String: Hostname

对d脚的回应：

Frame 18: 86 bytes on wire (688 bits), 86 bytes captured (688 bits)
    Encapsulation type: D-Bus (146)
    Arrival Time: Mar 13, 2024 07:21:04.048994000 AEDT
    [Time shift for this packet: 0.000000000 seconds]
    Epoch Time: 1710274864.048994000 seconds
    [Time delta from previous captured frame: 0.000376000 seconds]
    [Time delta from previous displayed frame: 0.000376000 seconds]
    [Time since reference or first frame: 2.547172000 seconds]
    Frame Number: 18
    Frame Length: 86 bytes (688 bits)
    Capture Length: 86 bytes (688 bits)
    [Frame is marked: False]
    [Frame is ignored: False]
    [Protocols in frame: dbus]
D-Bus
    Endianness: little-endian
    Message Type: Method reply
    Message Flags: 0x01
        .... ...1 = No Reply Expected: Not expected
        .... ..0. = No Auto Start: Start
        .... .0.. = Allow Interactive Authorization: Don't allow
    Protocol Version: 1
    Message Body Length: 22
    Message Serial: 10
    Header Field Array
        Array Length: 47
        Dict Entry, 5, Reply serial: 623
            Field Code: Reply serial (5)
            Variant: 623
                Variant Signature: u
                Reply serial: 623
        Dict Entry, 6, Destination: :1.83
            Field Code: Destination (6)
            Variant: :1.83
                Variant Signature: s
                Destination: :1.83
        Dict Entry, 8, Signature: v
            Field Code: Signature (8)
            Variant: v
                Variant Signature: g
                Signature: v
        Dict Entry, 7, Sender: :1.171
            Field Code: Sender (7)
            Variant: :1.171
                Variant Signature: s
                Sender: :1.171
    Body
        Variant: Lenny-Leonard
            Variant Signature: s
            String: Lenny-Leonard

Python 请求：

Frame 34: 197 bytes on wire (1576 bits), 197 bytes captured (1576 bits)
    Encapsulation type: D-Bus (146)
    Arrival Time: Mar 13, 2024 07:21:06.564106000 AEDT
    [Time shift for this packet: 0.000000000 seconds]
    Epoch Time: 1710274866.564106000 seconds
    [Time delta from previous captured frame: 0.000312000 seconds]
    [Time delta from previous displayed frame: 0.000312000 seconds]
    [Time since reference or first frame: 5.062284000 seconds]
    Frame Number: 34
    Frame Length: 197 bytes (1576 bits)
    Capture Length: 197 bytes (1576 bits)
    [Frame is marked: False]
    [Frame is ignored: False]
    [Protocols in frame: dbus]
D-Bus
    Endianness: little-endian
    Message Type: Method call
    Message Flags: 0x00
        .... ...0 = No Reply Expected: Expected
        .... ..0. = No Auto Start: Start
        .... .0.. = Allow Interactive Authorization: Don't allow
    Protocol Version: 1
    Message Body Length: 45
    Message Serial: 4
    Header Field Array
        Array Length: 135
        Dict Entry, 1, Path: /org/freedesktop/hostname1
            Field Code: Path (1)
            Variant: /org/freedesktop/hostname1
                Variant Signature: o
                Path: /org/freedesktop/hostname1
        Dict Entry, 6, Destination: :1.171
            Field Code: Destination (6)
            Variant: :1.171
                Variant Signature: s
                Destination: :1.171
        Dict Entry, 2, Interface: org.freedesktop.Dbus.Properties
            Field Code: Interface (2)
            Variant: org.freedesktop.Dbus.Properties
                Variant Signature: s
                Interface: org.freedesktop.Dbus.Properties
        Dict Entry, 3, Member: Get
            Field Code: Member (3)
            Variant: Get
                Variant Signature: s
                Member: Get
        Dict Entry, 8, Signature: ss
            Field Code: Signature (8)
            Variant: ss
                Variant Signature: g
                Signature: ss
        Dict Entry, 7, Sender: :1.173
            Field Code: Sender (7)
            Variant: :1.173
                Variant Signature: s
                Sender: :1.173
    Body
        String: org.freedesktop.hostname1
        String: Hostname

对Python的回应：

Frame 35: 189 bytes on wire (1512 bits), 189 bytes captured (1512 bits)
    Encapsulation type: D-Bus (146)
    Arrival Time: Mar 13, 2024 07:21:06.564291000 AEDT
    [Time shift for this packet: 0.000000000 seconds]
    Epoch Time: 1710274866.564291000 seconds
    [Time delta from previous captured frame: 0.000185000 seconds]
    [Time delta from previous displayed frame: 0.000185000 seconds]
    [Time since reference or first frame: 5.062469000 seconds]
    Frame Number: 35
    Frame Length: 189 bytes (1512 bits)
    Capture Length: 189 bytes (1512 bits)
    [Frame is marked: False]
    [Frame is ignored: False]
    [Protocols in frame: dbus]
D-Bus
    Endianness: little-endian
    Message Type: Error reply
    Message Flags: 0x01
        .... ...1 = No Reply Expected: Not expected
        .... ..0. = No Auto Start: Start
        .... .0.. = Allow Interactive Authorization: Don't allow
    Protocol Version: 1
    Message Body Length: 69
    Message Serial: 12
    Header Field Array
        Array Length: 103
        Dict Entry, 5, Reply serial: 4
            Field Code: Reply serial (5)
            Variant: 4
                Variant Signature: u
                Reply serial: 4
        Dict Entry, 6, Destination: :1.173
            Field Code: Destination (6)
            Variant: :1.173
                Variant Signature: s
                Destination: :1.173
        Dict Entry, 4, Error name: org.freedesktop.DBus.Error.UnknownMethod
            Field Code: Error name (4)
            Variant: org.freedesktop.DBus.Error.UnknownMethod
                Variant Signature: s
                Error name: org.freedesktop.DBus.Error.UnknownMethod
        Dict Entry, 8, Signature: s
            Field Code: Signature (8)
            Variant: s
                Variant Signature: g
                Signature: s
        Dict Entry, 7, Sender: :1.171
            Field Code: Sender (7)
            Variant: :1.171
                Variant Signature: s
                Sender: :1.171
    Body
        String: Unknown method Get or interface org.freedesktop.Dbus.Properties.

我在这里缺少什么？ 是否可以发送一些其他请求来发现哪些方法可用于所选接口和/或验证它是正确的接口？

谢谢。

python dbus
1个回答
0
投票

该问题已通过纠正 ukBaz 指出的拼写错误得到解决。

org.freedesktop.Dbus.Properties --> org.freedesktop.DBus.Properties

现在按预期工作。

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