Voice

Voice connections operate in a similar fashion to the Gateway connection. However, they use a different set of payloads and a separate UDP-based connection for voice data transmission. Because UDP is used for both receiving and transmitting voice data, your client must be able to receive UDP packets, even through a firewall or NAT (see UDP Hole Punching for more information). The Discord Voice servers implement functionality (see IP Discovery) for discovering the local machines remote UDP IP/Port, which can assist in some network configurations.

To ensure that you have the most up-to-date information, please use version 4. Otherwise, we cannot guarantee that the Opcodes documented here will reflect what you receive over the socket.

The first step in connecting to a voice server (and in turn, a guild's voice channel) is formulating a request that can be sent to the Gateway, which will return information about the voice server we will connect to. Because Discord's voice platform is widely distributed, users should never cache or save the results of this call. To inform the gateway of our intent to establish voice connectivity, we first send an Opcode 4 Gateway Voice State Update:

json
{
  "op": 4,
  "d": {
    "guild_id": "41771983423143937",
    "channel_id": "127121515262115840",
    "self_mute": false,
    "self_deaf": false
  }
}

If our request succeeded, the gateway will respond with two events—a Voice State Update event and a Voice Server Update event—meaning your library must properly wait for both events before continuing. The first will contain a new key, session_id, and the second will provide voice server information we can use to establish a new voice connection:

json
{
  "t": "VOICE_SERVER_UPDATE",
  "s": 2,
  "op": 0,
  "d": {
    "token": "my_token",
    "guild_id": "41771983423143937",
    "endpoint": "smart.loyal.discord.gg"
  }
}

With this information, we can move on to establishing a voice WebSocket connection.

Once we retrieve a session_id, token, and endpoint information, we can connect and handshake with the voice server over another secure WebSocket. Unlike the gateway endpoint we receive in an HTTP Get Gateway request, the endpoint received from our Voice Server Update payload does not contain a URL protocol, so some libraries may require manually prepending it with "wss://" before connecting. Once connected to the voice WebSocket endpoint, we can send an Opcode 0 Identify payload with our server_id, user_id, session_id, and token:

json
{
  "op": 0,
  "d": {
    "server_id": "41771983423143937",
    "user_id": "104694319306248192",
    "session_id": "my_session_id",
    "token": "my_token"
  }
}

The voice server should respond with an Opcode 2 Ready payload, which informs us of the SSRC, UDP IP/port, and supported encryption modes the voice server expects:

json
{
  "op": 2,
  "d": {
    "ssrc": 1,
    "ip": "127.0.0.1",
    "port": 1234,
    "modes": ["xsalsa20_poly1305", "xsalsa20_poly1305_suffix", "xsalsa20_poly1305_lite"],
    "heartbeat_interval": 1
  }
}

In order to maintain your WebSocket connection, you need to continuously send heartbeats at the interval determined in Opcode 8 Hello:

json
{
  "heartbeat_interval": 41250
}

json
{
  "op": 8,
  "d": {
    "heartbeat_interval": 41250
  }
}

This is sent at the start of the connection. Be warned that the Opcode 8 Hello structure differs by gateway version as shown in the above examples. Versions below v3 do not have an opcode or a data field denoted by d. V3 and above was updated to be structured like other payloads. Be sure to expect this different format based on your version.

After receiving Opcode 8 Hello, you should send Opcode 3 Heartbeat—which contains an integer nonce—every elapsed interval:

json
{
  "op": 3,
  "d": 1501184119561
}

In return, you will be sent back an Opcode 6 Heartbeat ACK that contains the previously sent nonce:

json
{
  "op": 6,
  "d": 1501184119561
}

Once we receive the properties of a UDP voice server from our Opcode 2 Ready payload, we can proceed to the final step of voice connections, which entails establishing and handshaking a UDP connection for voice data. First, we open a UDP connection to the IP and port provided in the Ready payload. If required, we can now perform an IP Discovery using this connection. Once we've fully discovered our external IP and UDP port, we can then tell the voice WebSocket what it is, and start receiving/sending data. We do this using Opcode 1 Select Protocol:

json
{
  "op": 1,
  "d": {
    "protocol": "udp",
    "data": {
      "address": "127.0.0.1",
      "port": 1337,
      "mode": "xsalsa20_poly1305_lite"
    }
  }
}

Finally, the voice server will respond with a Opcode 4 Session Description that includes the mode and secret_key, a 32 byte array used for encrypting and sending voice data:

json
{
    "op": 4,
    "d": {
        "mode": "xsalsa20_poly1305_lite",
        "secret_key": [ ...251, 100, 11...]
    }
}

We can now start encrypting and sending voice data over the previously established UDP connection.

Voice data sent to discord should be encoded with Opus, using two channels (stereo) and a sample rate of 48kHz. Voice Data is sent using a RTP Header, followed by encrypted Opus audio data. Voice encryption uses the key passed in Opcode 4 Session Description and the nonce formed with the 12 byte header appended with 12 null bytes to achieve the 24 required by xsalsa20_poly1305. Discord encrypts with the libsodium encryption library.

To notify clients that you are speaking or have stopped speaking, send an Opcode 5 Speaking payload:

The following flags can be used as a bitwise mask. For example 5 would be priority and voice.

json
{
  "op": 5,
  "d": {
    "speaking": 5,
    "delay": 0,
    "ssrc": 1
  }
}

When there's a break in the sent data, the packet transmission shouldn't simply stop. Instead, send five frames of silence (0xF8, 0xFF, 0xFE) before stopping to avoid unintended Opus interpolation with subsequent transmissions.

When your client detects that its connection has been severed, it should open a new WebSocket connection. Once the new connection has been opened, your client should send an Opcode 7 Resume payload:

json
{
  "op": 7,
  "d": {
    "server_id": "41771983423143937",
    "session_id": "my_session_id",
    "token": "my_token"
  }
}

If successful, the Voice server will respond with an Opcode 9 Resumed to signal that your client is now resumed:

json
{
  "op": 9,
  "d": null
}

If the resume is unsuccessful—for example, due to an invalid session—the WebSocket connection will close with the appropriate close event code. You should then follow the Connecting flow to reconnect.

Generally routers on the Internet mask or obfuscate UDP ports through a process called NAT. Most users who implement voice will want to utilize IP discovery to find their external IP and port which will then be used for receiving voice communications. To retrieve your external IP and port, send the following UDP packet to your voice port (all numeric are big endian):