streams

Streams

Uses Java's Input and OutputStreams and simple text-based protocol:

MessageChannel channel = new StreamsMessageChannel(System.in, System.out);
channel.addListener(TextMessage.class, msg -> {
    ...
});
channel.start();
channel.send("Hello");

Can be used with stdout/stderr, TCP sockets etc. If used over TCP then netcat or socat command-line tools can be used to debug. Telnet does not work, because it uses ASCII, not UTF-8.

More examples here

Protocol

• text-based - text messages are encoded as is, binary ones using Base64 encoding (useful for debugging purposes)

• uses UTF-8 encoding (always)

• every message is a line (sequence of characters with EOL \n on the end)

• text message is encoded as is or with # character prefix, e.g.:

  some message\n decodes to some message

  #some message\n decodes to some message

  ##some message\n decodes to #some message

• binary message is encoded using Base64 always with $ character prefix, e.g.:

  $AQID\n decodes to [1,2,3]

• multi-line text message is encoded with @ character prefix. EOL is no longer a message end. Line .\n should be used instead

     @Multi-line\n
     text message\n
     .\n
  

  decodes to

     Multi-line
     text message
  

  • if some line in multi-line text message starts with a dot . then the whole line should be prefixed with another dot:

       @Multi-line message with a dot in following line\n
       ..\n
       .\n
    

    decodes to

       Multi-line message with a dot in following line
       .