Integration / D Bus Interview Questions
What is the difference between a D-Bus method call and a signal?
A method call is directed and expects a response: the caller names a specific destination service, object path, and interface, and the bus daemon routes the call there and back, with the caller typically waiting for a method return or an error.
A signal is undirected and expects no response: it's emitted by an object without naming a destination, and the bus daemon broadcasts it to every connection that has registered a matching match rule. The sender doesn't know or care who, if anyone, is listening.
| Method call | Signal |
| Directed to one destination | Broadcast to any matching subscriber |
| Expects a reply or error | No reply expected |
| Used to request an action | Used to announce that something happened |
A method call differs from a signal mainly because it:
A signal is delivered to:
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