IpcOneShotServer::accept is blocking and has no non-blocking version

[pYtoner]

A non-blocking version is needed to be used in an async context.
Something like IpcOneShotServer::try_accept()

If you think this is not too difficult for someone, who is very new to this lib, to implement this then I would happily do it.

What return type would make sense?

[tevoinea]

I'd like a non-blocking accept as well. What I was thinking was:

1. Create a try_accept in OsIpcOneShotServer that calls try_recv on the OsIpcReceiver
2. Create try_accept in IpcOneShotServer that uses the newly created try_accept from step 1

Return types shouldn't need to change since they already return Result.

I'm also happy to open a PR for this if the maintainers will accept the contribution!

[jdm]

I'd review a PR that added that implementation if you verify that it works as expected!

[glyn]

I'd like a non-blocking accept as well. What I was thinking was:

1. Create a `try_accept` in `OsIpcOneShotServer` that calls `try_recv` on the `OsIpcReceiver`

try_accept on Unix variants would also need to avoid blocking waiting for a connect request (in libc::accept).

2. Create `try_accept` in `IpcOneShotServer` that uses the newly created `try_accept` from step 1

Return types shouldn't need to change since they already return Result.

I think there would need to be a change of return types. Consider the Unix behaviour. The current return type:

Result<(IpcReceiver<T>, T), bincode::Error>

does not cope with the case where a connect request was available when accept was called. In that case a connection is formed and a receiver can be constructed, but if there is no message available from the receiver, accept needs to return the receiver but no message. The current signature only allows an error to be returned if there is no message available. But that would mean the receiver and the underlying connection will be discarded, rather than returned to allow messages to be received.

I'm also happy to open a PR for this if the maintainers will accept the contribution!