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Portal is a unified REPL and command server for Clojure.

Protocol

Portal uses netstrings to encode messages1. This makes client implementations as simple as possible. The format of an individual message is as follows:

id type data

The id is a string identifier used to determine which evaluation context to use. The context is used to maintain state across multiple commands and has a unique stdin, stdout and stderr from other contexts. It is helpful to think of each context as executing in a dedicated thread, though actually agents are used to implement contexts, so a thread pool is shared among all contexts.

In addition, all commands within a given context are serialized so they happen in the order they are received, and one command cannot start until the previous command for that context finishes. Of course, you can call commands asynchronously though by using unique ids.

For client requests type can be one of:

  • eval - Evaluate the forms provided in data.
  • stdin - Write the string provided in data to *in*.
  • clear - Clear the context for id.
  • fork - Associate the context for id with the id provided in data.

For server responses type can be one of:

  • result - Evaluation completed with no errors. The results are provided in data
  • error - There was an exception during evaluation. The error type and message are provided in data.
  • read-error - There was an error while reading the forms. The error message is provided in data.
  • stdout - The string in data was printed to *out* during evaluation.
  • stderr - The string in data was printed to *err* during evaluation.

Client Libraries

  • Ruby
  • Clojure (coming soon)
  • elisp (coming soon)
  • Haskell (coming soon)
  • Your favorite language (patches welcome...)
  1. Thanks to James Reeves for this suggestion. ↩