signal-cli provides a JSON-RPC based API with the jsonRpc and daemon commands.

• jsonRpc command accepts input on STDIN and responds on STDOUT. This is intended to make it easier to embed signal-cli in other applications.

  signal-cli -a _ACCOUNT_ jsonRpc or for multi-account mode signal-cli jsonRpc

• daemon command provides a UNIX or TCP socket and can handle requests from multiple clients.

  signal-cli -a _ACCOUNT_ daemon --socket or for multi-account mode signal-cli daemon --socket

See the corresponding man page for more information.