Stream Audio Into a Call with Java

This is the code for the Nexmo Developer blog post of the same name. It shows you how to create a conference and then stream audio into it.

Configure and run the application by executing the following steps:

Install the Nexmo CLI

This step requires npm (the Node Package Manager), which is part of Node.js.

Run the following command, replacing NEXMO_API_KEY and NEXMO_API_SECRET with your API key and secret in the Developer Dashboard:

npm install -g nexmo-cli
nexmo setup NEXMO_API_KEY NEXMO_API_SECRET

Buy a Nexmo Virtual number

Search for available numbers with voice capability, using your two-character country code. For example, using GB for the United Kingdom:

nexmo number:search GB --voice --verbose

Buy one of the numbers, for example 442079460000:

nexmo number:buy 442079460000

Run ngrok

Your webhooks must be publicly accessible over the Internet. You can use ngrok for this (see our blog post on ngrok).

Run ngrok on port 3000 using the following command and make a note of the URLs it creates for you:

ngrok http 3000

Create a Voice API application

Run the following command in the project's root directory, replacing the /webhooks/answer URL domain name with the one provided by ngrok. We don't use /webhooks/events in this example, so provide any URL for that.

nexmo app:create "Play Call Audio" https://41acbcd0.ngrok.io/webhooks/answer https://example.com/webhooks/events --keyfile private.key

Make a note of the application ID. This step also downloads your Nexmo credentials in a file called private.key.

Link your Nexmo number to your Voice Application

Replace NEXMO_APPLICATION_ID with the one returned by the preceding command.

nexmo link:app NEXMO_NUMBER NEXMO_APPLICATION_ID

Configure the application

Copy example.env to .env. Replace the NEXMO_APPLICATION_ID with your own application ID. If you have followed the steps above you can leave the other settings unchanged.

Run the application

1. Execute gradle run.

2. Dial your Nexmo number.

3. When the call is answered, you should hear a short welcome message.

4. Copy the call ID that is shown in the console.

5. In your browser's address bar, enter http://localhost:3000/play/, followed by the call ID.

6. The audio at AUDIO_URL should be streamed into the call and terminated after the number of milliseconds specified in AUDIO_DURATION_MSEC.