Taking a fact from an agent, arvo or whatever is easy. First you subscribe using watch:strandio or watch-our:strandio, then you use take-fact:strandio to receive the fact. Here's an example that takes an update from graph-store and prints the message to the dojo:

print-msg.hoon

/-  spider
/+  *strandio, *graph-store
=,  strand=strand:spider
=>
|%
++  take-update
  =/  m  (strand ,~)
  ^-  form:m
  ;<  =cage  bind:m  (take-fact /graph-store)
  =/  =update  !<  update  q.cage
  ?.  ?=(%add-nodes -.q.update)
    (pure:m ~)
  =/  nodes=(list [=index =node])  ~(tap by nodes.q.update)
  ?~  nodes
    (pure:m ~)
  =/  contents=(list content)  contents.post.node.i.nodes
  ?~  contents
    (pure:m ~)
  ?.  ?=(%text -.i.contents)
    (pure:m ~)
  =/  msg  (trip text.i.contents)
  %-  (slog leaf+msg ~)
  (pure:m ~)
--
^-  thread:spider
|=  arg=vase
=/  m  (strand ,vase)
^-  form:m
;<  ~        bind:m  (watch-our /graph-store %graph-store /updates)
;<  ~        bind:m  take-update
(pure:m !>(~))

Create a chat on your fake zod if you don't have one already, then save the thread in /ted on the %base desk, |commit %base, and run -print-msg. Next, type some message in your chat and you'll see it printed in the dojo.

Analysis

First we call watch-our to subscribe:

;<  ~        bind:m  (watch-our /graph-store %graph-store /updates)

We've spun the next part out into its own core, but it's just a take-fact to receive the update:

  ;<  =cage  bind:m  (take-fact /graph-store)

The rest of the code is just to pull the message out of the complicate data structure returned by graph-store and isn't important.

Spider will automatically leave the subscription once the thread finishes.

Note that take-fact only takes a single fact, so you'd need one for each message you're expecting. Alternatively you can use main-loop to take an arbitrary number of facts.