Live API and the browser live view

12.1 What you need#

• A licence that includes the Live API. Without it the Live API tab does not appear in the Settings window.
• The computer running Pulse Monitor and the devices that watch in the same network — wired or Wi-Fi, for example the club’s router. The devices need a browser; a smart TV, a tablet, a phone and any computer will do.
• Windows Firewall must allow Pulse Monitor to receive connections (Windows Firewall).

12.2 Switching it on#

1. Open Settings → Live API (Settings).

   

2. Tick Publish live training data on the local network. The program asks for a confirmation: During trainings, the participants’ heart rate data will be available on your local network to anyone who has the access key. Do you confirm that the participants have been informed and that you are entitled to share their data? Answer Yes only if that is so (Privacy and personal data).

3. Click Test port (Test port).

4. Click Save.

The connection is encrypted by default. The first time a browser opens the link it warns about the certificate — this is normal and is explained in Encryption and the certificate.

The tab shows everything you need to connect:

12.3 The “Live:” indicator#

When the Live API is on, the bottom bar of the live screen shows Live: and a small coloured disc:

12.4 Watching in a browser#

Open the link from the Address field in the browser of any device in the same network, for example on a TV:

https://192.168.1.15:8765/?key=K7MH3RAW

The first time, the browser warns that the connection is not trusted — see Encryption and the certificate for what to click.

The page shows the participants as boxes — like the training screen: the nickname, the heart rate, the calories, the percentage of the maximum heart rate and the zone colour in the background. A grey box with dashes is a participant without a signal. A small check the belt at the bottom of a box is the same warning as on the training screen (Monitor sensor contact).

• The title bar shows the name of the training (Drop-in for a Drop-in session), the bottom bar the status, the time of the training and the Start / Stop button.
• The boxes fit the screen: the page chooses the number of columns and rows so that all participants are visible. Up to 42 participants are shown; on a very small screen the page scrolls.
• For a full screen use the browser’s full-screen key (usually F11).
• The status next to the button tells what is happening: ok (data arrives), waiting for training (the program works but there is nothing to show yet), no new data (the transmission stopped — the training screen was closed, or the sensors were lost), cannot connect (the page retries by itself), wrong key.

The page remembers the address and the key in that browser. The icon in its top right corner (Forget this connection) removes them again. If you open https://192.168.1.15:8765/ without the key, the page asks for the address and the key and connects when you click Connect.

12.5 The access key#

The access key is what allows a device to read the data: whoever has the key can watch your trainings as long as a live screen is open.

• It has eight characters from a set that avoids look-alikes (no 0 and O, no 1 and I and L), so it is easy to dictate and to type on a TV remote. Capital letters, small letters, spaces and dashes do not matter: k7mh 3raw is the same key.
• Copy copies the key as one string, without the space.
• New key makes a new key after a confirmation (Generate a new key? Anyone using the old key will stop receiving data.). Click Save to apply it. The devices that use the old key stop receiving data; give the new one to the others. Do this whenever the key may have got to the wrong person.
• A device that sends a wrong key five times is blocked for one minute. A person who mistyped the key once or twice is not affected.

12.6 Encryption and the certificate#

Everything the program sends — the page, the data and the live stream — is encrypted (HTTPS and WSS), so that someone who only watches the traffic of the network cannot read the heart rates. This is switched on by default and you do not have to do anything for it.

The encryption needs a certificate. Pulse Monitor makes its own on your computer the first time it is needed. Nobody can issue an official certificate for the private address of a computer, so a browser does not know this one in advance and warns about it. The warning does not mean that something is wrong — it means that the certificate is not from a public authority. You accept it once for each browser:

The browser remembers the choice for that address, so the next time the page opens at once. A page that Pulse Monitor itself serves needs no more than this — its data connection works with the same choice.

12.7 What is published#

For each participant on the screen: the nickname (not the full name), the heart rate, the percentage of the maximum heart rate, the calories burned so far, the zone colour, and whether the sensor has a signal or the belt needs checking. For the training: its name and the time. Only the current values are published — there is no history and nothing is saved by the Live API.

12.8 Windows Firewall#

The first time Pulse Monitor opens the port, Windows asks whether it may receive connections. In the window that appears:

1. Tick Private networks (the club’s network at home or at work).
2. Leave Public networks unticked, unless the club’s network is a public one and you know why.
3. Click Allow access.

If you clicked Cancel, or the devices cannot connect, the permission is missing. To give it:

1. Open Windows Security → Firewall & network protection → Allow an app through firewall.
2. Click Change settings.
3. Find Pulse Monitor in the list and tick Private. If it is not on the list, click Allow another app… and choose PulseMonitor5.exe from the folder where Pulse Monitor is installed.
4. Click OK.

12.9 Troubleshooting#

12.10 For developers#

The same data can be read by your own program. Here is the short version.

The most accurate and up-to-date documentation of the Live API, including the data format and example clients in several languages, is available at https://github.com/radeal-eu/pulselive.

The addresses are https://… and wss://… (http://… and ws://… when the encryption is turned off). The certificate is self-signed, so a program should compare its SHA-256 fingerprint with the one shown in Settings → Live API instead of switching the check off. The key can also be sent in the header Authorization: Bearer …. A snapshot contains the complete state, so the last one is all that is needed:

{
  "v": 1,
  "seq": 1234,
  "sentAt": "2026-10-15T18:30:01Z",
  "training": { "name": "Spinning 18:00", "elapsedSec": 1834 },
  "participants": [
    {
      "nick": "Ania",
      "color": "#FF8800",
      "hr": 142,
      "pctMax": 78,
      "kcal": 312,
      "signal": true,
      "checkBelt": false
    }
  ]
}

sentAt changes with every snapshot; when it stops changing, nothing is being published. Up to 20 devices can be connected to the live stream (/ws) at the same time — the browser view uses it, so each open browser page counts as one device. Reading /live with ordinary requests does not count towards this limit.