[Home](./index.md) > [sip.js](./sip.js.md) > [Transport](./sip.js.transport.md) > [onMessage](./sip.js.transport.onmessage.md) ## Transport.onMessage property Callback on receipt of a message. Signature: ```typescript onMessage: ((message: string) => void) | undefined; ``` ## Remarks When the `UserAgent` is constructed, this property is set. The `state` MUST be "Connected" when this is called.