Socket protocol:

- Client sends a non-zero length record ID string.
- Client sends a series of non-zero-length strings.
- Client sends a zero-length string.
- Server sends an single acknowledgement byte and closes the socket.
  That byte will be non-zero for success, or zero on error.

Notes:

- All numbers are represented as 4-byte binary MSB first.

- A "string" above is represented as a length number followed
  immediately by that many bytes of data.

- It is assumed that the client has written the data to a permanent file
  store (asynchronously) before sending it to the journalling process.