Input and output folder

With an input/output folder orchestration 1 publishes the message in the MesssageBox. A send port subscribes to this message and writes it to a file. A receive location reads the file and publishes to the MessageBox where orchestration 2 subscribes to the message.
Apart from the overhead of doing this you may hit file contention issues if your files are large.
Having orchestration 2 subscribe to the message published by orchestration 1 cuts out unnecessary work.
This is achieved by using Direct ports.
Care must be taken when using direct ports. If you declare a direct port in an orchestration by default it will subscribe to every message that matches the message type declared in the receive shape. You can add filters to that receive shape to subscribe to a subset of messages. You can filter on any promoted property in the message context.