Add documentation to contrib folder

This commit adds brief documentation for this feature.  Included in the
justification is the purpose of this feature as well as usage and
functionality tips.

1 files changed, 25 insertions, 0 deletions

diff --git a/contrib/message-capture/message-capture-docs.md b/contrib/message-capture/message-capture-docs.md
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+# Per-Peer Message Capture
+
+## Purpose
+
+This feature allows for message capture on a per-peer basis.  It answers the simple question: "Can I see what messages my node is sending and receiving?"
+
+## Usage and Functionality
+
+* Run `bitcoind` with the `-capturemessages` option.
+* Look in the `message_capture` folder in your datadir.
+  * Typically this will be `~/.bitcoin/message_capture`.
+  * See that there are many folders inside, one for each peer names with its IP address and port.
+  * Inside each peer's folder there are two `.dat` files: one is for received messages (`msgs_recv.dat`) and the other is for sent messages (`msgs_sent.dat`).
+* Run `contrib/message-capture/message-capture-parser.py` with the proper arguments.
+  * See the `-h` option for help.
+  * To see all messages, both sent and received, for all peers use:
+    ```
+    ./contrib/message-capture/message-capture-parser.py -o out.json \
+    ~/.bitcoin/message_capture/**/*.dat
+    ```
+  * Note:  The messages in the given `.dat` files will be interleaved in chronological order.  So, giving both received and sent `.dat` files (as above with `*.dat`) will result in all messages being interleaved in chronological order.
+  * If an output file is not provided (i.e. the `-o` option is not used), then the output prints to `stdout`.
+* View the resulting output.
+  * The output file is `JSON` formatted.
+  * Suggestion: use `jq` to view the output, with `jq . out.json`