protocol.md

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How to develop a protocol type plugin

This guide will introduce how to develop a protocol type plugin that does not depend on a configuration file.

To develop a protocol type plugin, you need to implement at least the following two sub-functions:

• Implement codec.Framer and codec.FramerBuilder interfaces to read the complete business package from the connection
• Implement codec.Codec interface to parse the binary request body from the complete binary network data package and package the binary response body into a complete binary network data package

In addition, depending on the specific protocol, you may also need to implement codec.Serializer and codec.Compressor interfaces.

The following uses the implementation of the "rawstring" protocol in trpc-codec as an example to introduce the related development steps. More specific code can be found here.

The "rawstring" protocol is a simple communication protocol based on tcp, characterized by using the "\n" character as the delimiter for sending and receiving packets.

Implement codec.Framer and codec.FramerBuilder interfaces

type FramerBuilder struct{}

func (fd *FramerBuilder) New(reader io.Reader) transport.Framer {
    return &framer{
        reader: reader,
    }
}

type framer struct {
    reader io.Reader
}

func (f *framer) ReadFrame() (msg []byte, err error) {
    reader := bufio.NewReader(f.reader)
    return reader.ReadBytes('\n')
}

Register the implemented FramerBuilder to the transport package

var DefaultFramerBuilder = &FramerBuilder{}
func init() {
    transport.RegisterFramerBuilder("rawstring", DefaultFramerBuilder)
}

Implement codec.Codec interface

Implement server-side Codec

type serverCodec struct{}

func (sc *serverCodec) Decode(_ codec.Msg, req []byte) ([]byte, error) {
    return req, nil
}

func (sc *serverCodec) Encode(_ codec.Msg, rsp []byte) ([]byte, error) {
    return []byte(string(rsp) + "\n"), nil
}

Implement client-side Codec

type clientCodec struct{}

func (cc *clientCodec) Encode(_ codec.Msg, reqBody []byte) ([]byte, error) {
    return []byte(string(reqBody) + "\n"), nil
}

func (cc *clientCodec) Decode(_ codec.Msg, rspBody []byte) ([]byte, error) {
    return rspBody, nil
}

Register the implemented Codec to the codec package

func init() {
	codec.Register("rawstring", &serverCodec{}, &clientCodec{})
}

More examples

For more examples, you can refer to the trpc-codec code repository