On call TypeError: Cannot read properties of undefined (reading 'sendMessage')

[avct-net]

Hello,
KMS is a new technology for me.
I installed a kurento-media-server 7.0. on debian 11.
I access the one2one-call interface correctly.
I can register users.
but when I run the first call I get the following error message :

/home/vincent/kurento/tutorials/javascript-node/one2one-call/server.js:411
    caller.sendMessage(message);

TypeError: Cannot read properties of undefined (reading 'sendMessage')
    at call (/home/vincent/kurento/tutorials/javascript-node/one2one-call/server.js:411:12)
    at WebSocket.<anonymous> (/home/vincent/kurento/tutorials/javascript-node/one2one-call/server.js:245:13)
    at WebSocket.emit (node:events:514:28)
    at WebSocket.emit (node:domain:489:12)
    at Receiver.receiverOnMessage (/home/vincent/kurento/tutorials/javascript-node/one2one-call/node_modules/ws/lib/websocket.js:1068:20)
    at Receiver.emit (node:events:514:28)
    at Receiver.emit (node:domain:489:12)
    at Receiver.dataMessage (/home/vincent/kurento/tutorials/javascript-node/one2one-call/node_modules/ws/lib/receiver.js:517:14)
    at Receiver.getData (/home/vincent/kurento/tutorials/javascript-node/one2one-call/node_modules/ws/lib/receiver.js:435:17)
    at Receiver.startLoop (/home/vincent/kurento/tutorials/javascript-node/one2one-call/node_modules/ws/lib/receiver.js:143:22)

[avct-net]

when I throw
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