Often, a message is being sent and followed by a call to `recv`
to wait for a reply. Create a simple helper `send_and_recv` that
does both in one method.
Add a simple check for that helper to the tests.
Add a new constructor method that allows creating a `Socket` from
an existing file-descriptor of a socket. This might be need when
the socket was passed to a child process.
Add a simple test for the new constructor method.
Add a new constructor method, `Socket.new_pair`, to create a pair
of connected sockets (via `socketpair`) and wrap both sides via
`jsoncomm.Socket`.
Add a simple test to check it.
Now that jsoncomm.Socket is using a connection-oriented socket,
the destination in `socket.sendmsg` is ignored and thus can and
should be dropped from the `jsoncomm.Socket.send` method.
Adjust the tests accordingly.
Switch to use a connection oriented datagram based protocol, i.e.
`SOCK_SEQPACKET`, instead of `SOCK_DGRAM`. It sill preserves
message boundaries, but since it is connection oriented the client
nor the server do not need to specify the destination addresses
of the peer in sendmsg/recvmesg. Moreover, the host will be able
to send messages to the client, even if the latter is sandboxed
with a separate network namespace. In the `SOCK_DRAM` case the
auto-bound address of the client would not be visible to the host
and thus sending messages would to it would fail.
Adapt the jsoncomm tests as well as `BaseAPI`.
Add support for `util.types.PathLike` paths for socket addresses,
instead of just plain strings. Test it by using pathlib.Path to
create the address in the corresponding test.
