###--希望能成功实现！
###--It is planned to add the transmission function of DTMF signals on the basis of the original AudioSocket. It will not actually generate and detect DTMF information. This function needs to be implemented at the other end of the network.
###--Hope it can be achieved successfully!
AudioSocket is a simple TCP-based protocol for sending and receiving realtime audio streams.
There exists a protocol definition (below), a Go library, and Asterisk application and channel interfaces.
NOTE: as of 2020-01-15, AudioSocket has been included in the upstream Asterisk system. While I am leaving the Asterisk patches here for use with previous versions, the Asterisk code in this repository should be considered obsolete. The Go code is up-to-date, maintained, and this is the primary source for it.
The singular design goal of AudioSocket is to present the simplest possible audio streaming protocol, initially based on the constraints of Asterisk audio. Each packet contains a three-byte header and a variable payload. The header is composed of a one-byte type and a two-byte length indicator.
The minimum message length is three bytes: type and payload-length. Hangup
indication, for instance, is 0x00 0x00 0x00.
0x00- Terminate the connection (socket closure is also sufficient)0x01- Payload will contain the UUID (16-byte binary representation) for the audio stream0x02- Payload is Dtmf start & stop signal, total 6 bytes. 1 byte state: 1:start dtmf, 0:stop dtmf; 1 byte code , 1-9, *, #, A-D; 4 bytes int duration, little-endian (0 for dtmf begin)0x03- Payload is AST_CONTROL_(ANSWER RING BUSY HANGUP ....see frame.h ) base control signal, 1 byte.0x10- Payload is signed linear, 16-bit, 8kHz, mono PCM (little-endian)0xff- An error has occurred; payload is the (optional) application-specific error code. Asterisk-generated error codes are listed below.
The payload length is a 16-bit unsigned integer (big endian) indicating how many bytes are in the payload.
The content of the payload is defined by the header: type and length.
Error codes are application-specific. The error codes for Asterisk are single-byte, bit-packed error codes:
0x01- hangup of calling party0x02- frame forwarding error0x04- memory (allocation) error
There are two Asterisk implementations: a channel interface and a dialplan application interface. Each of these lends itself to simplify a different use-case, but they work in exactly the same way.
The following examples demonstrate an AudioSocket connection to a server at
server.example.com running on TCP port 9092. The UUID (which is chosen
arbitrarily) of the call is 40325ec2-5efd-4bd3-805f-53576e581d13.
Dialplan application:
exten = 100,1,Verbose("Call to AudioSocket via Dialplan Application")
same = n,Answer()
same = n,AudioSocket(40325ec2-5efd-4bd3-805f-53576e581d13,server.example.com:9092)
same = n,Hangup()
Channel interface:
exten = 101,1,Verbose("Call to AudioSocket via Channel interface")
same = n,Answer()
same = n,Dial(AudioSocket/server.example.com:9092/40325ec2-5efd-4bd3-805f-53576e581d13)
same = n,Hangup()