speech-dispatcher: Communication mechanisms
3.1 Communication mechanisms
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Speech Dispatcher supports two communication mechanisms: UNIX-style and
Inet sockets, which are refered as 'unix-socket' and 'inet-socket'
respectively. The communication mechanism is decided on startup and
cannot be changed at runtime. Unix sockets are now the default and
preferred variant for local communication, Inet sockets are necessary
for communication over network.
The mechanism for the decision of which method to use is as follows
in this order of precedence: command-line option, configuration option,
the default value 'unix-socket'.
_Unix sockets_ are associated with a file in the filesystem. By
default, this file is placed in the user's runtime directory (as
determined by the value of the XDG_RUNTIME_DIR environment variable and
the system configuration for the given user). It's default name is
constructed as 'XDG_RUNTIME_DIR/speech-dispatcher/speechd.sock'. The
access permissions for this file are set to 600 so that it's restricted
to read/write by the current user.
As such, access is handled properly and there are no conflicts
between the different instances of Speech Dispatcher run by the
different users.
Client applications and libraries are supposed to independently
replicate the process of construction of the socket path and connect to
it, thus establishing a common communication channel in the default
setup.
It should be however possible in the client libraries and is possible
in the server, to define a custom file as a socket name if needed.
Client libraries should respect the SPEECHD_ADDRESS environment
variable.
_Inet sockets_ are based on communication over a given port on the
given host, two variables which must be previously agreed between the
server and client before a connection can be established. The only
implicit security restriction is the server configuration option which
can allow or disallow access from machines other than localhost.
By convention, the clients should use host and port given by one of
the following sources in the following order of precedence: its own
configuration, value of the SPEECHD_ADDRESS environment variable and the
default pair (localhost, 6560).
⇒Setting Communication Method.
Info Catalog
speech-dispatcher: Technical Specifications
speech-dispatcher: Technical Specifications
speech-dispatcher: Address specification