JMRI: LCC Traffic Monitor Window
Author: Bob Jacobsen
Keywords: JMRI help monitor

# LCC Traffic Monitor Window

JMRI provides a communications monitor window so you can see what's happening on the LCC network.

Once you open a monitor window, it will automatically display all traffic on the network as long as "Filter Bytes" is blank.

## Controls

Copy to clipboard
  Copies the log area to the system clipboard.
Clear Screen
  Erases the log area at the top of the screen.
Freeze Screen
  Stops acquiring new information, so that the captured information stops scrolling up.
Show raw data
  Normally, the monitor displays the program's interpretation of what it's seeing. If you want to see the raw bytes, check this box.
Show timestamps
  Normally, the program just displays the data from the communication link. If you'd like each message to be preceded by the time it was sent or received, check this box.
Window always on top
  This window will stay on top of other ones as you move windows around.
Auto scroll
  Scroll the contents of the window up so that the most recent traffic is visible at the bottom. If you manually scroll the window, e.g. to look at something, the auto-scroll will pause until you bring the window back down to the bottom.
Show Name for Node
  Display node names in addition to their numeric IDs. This takes an extra line on the display, so we make it optional.
Event (First)
  Event IDs can have name and navigation information associated with them. When this box is checked, only the first of those will be displayed. This takes less space on the display than showing them all.
Event (All)
  Show all the information that's associated with an event ID.
Filter Bytes
  You can filter unwanted messages from the window by entering each message's first hex value(s) into the "Filter Bytes" field. This can be especially helpful when there is a lot of routine comm traffic. Separate multiple values by spaces. e.g. "195B4 19544". This example will suppress any messages whose raw data starts with "195B4" or "19544". You can determine the appropriate hex values by turning on "Show raw data."
Add to Log
  If you want to insert a message into the captured information, e.g. to make a note about what you're about to do, you can type it into the text field next to the "Add Message" button and then click that button. This is particularly useful when you're logging to a file (see below) and want to make a note for later about what's happening.

## Logging To A File

Sometimes, it's helpful to capture what's happening. For example, you might encounter a bug (!!), and want to send a copy of what's happening to the people who are trying to fix it.

Small amounts of data can be copied from the log window with your computers "copy" command (e.g. ctrl-C or cmd-C), and then pasted into an email.

If you want to capture more, you can have the window write a log file on your computer's disk. To do this:

1. Click "Choose log file". A file-chooser window will open. Navigate to where you want to store the file, enter a name for the new log file, and click "Save". Note that if you pick a file that already exists, it will be overwritten.
2. When you're ready to capture the data you want, click "Start logging" on the monitor window.
3. When you're done, click "Stop logging" to store the data and close the file.

## Interpreting the Output

A simple message with all options on might be listed like: `

    17:49:57.335: [[19968a90] 03 19                  ]  S: 02.01.12.FE.77.16 - 09.00.99.03.00.35 Identify Events
      Src: JMRI - LccPro    Dest: TCS CS-105, S/N 0035

` Interpreting this from left to right:

- "17:49:57.335" is the local time that the message was processed
- "`[[19968a90] 03 19 ]`" is the contents of the CAN frame that was received in this case.
- "S:" indicates this was sent by JMRI; R: indicates it was received by JMRI; if you're running an OpenLCB/LCC hub, traffic from the hub will be indicated by H:
- "02.01.12.FE.77.16" is the node ID of the sending node, in this case JMRI
- "09.00.99.03.00.35" is the node ID of the destination node. If this is a global message, this will be blank
- "Identify Events" is the interpretation of the message. This field might be quite long.
- On the next line, "Src: JMRI - LccPro " is the name of the source node.
- "Dest: TCS CS-105, S/N 0035" is the name of the destination node.

Messages that carry event IDs may have extra lines to carry additional information about the event.