# Protocol Multiplexing using rpc-style multicodecs, protobufs with libp2p
# Protocol Multiplexing using rpc-style multicodecs, protobufs with libp2p
This examples shows how to use multicodecs (i.e. protobufs) to encode and transmit information between LibP2P hosts using LibP2P Streams.
This examples shows how to use multicodecs (i.e. protobufs) to encode and transmit information between LibP2P hosts using LibP2P Streams.
Multicodecs present a common interface, making it very easy to swap the codec implementation if needed.
Multicodecs present a common interface, making it very easy to swap the codec implementation if needed.
This example expects that you area already familiar with the [echo example](https://github.com/libp2p/go-libp2p/tree/master/examples/echo).
This example expects that you area already familiar with the [echo example](https://github.com/libp2p/go-libp2p/tree/master/examples/echo).
## Build
## Build
Compile the .proto files with the protobufs go compiler:
Compile the .proto files using the protobufs go compiler:
```
```
protoc --go_out=. ./p2p.proto
protoc --go_out=. ./p2p.proto
...
@@ -31,8 +29,9 @@ From `multipro` base source folder:
...
@@ -31,8 +29,9 @@ From `multipro` base source folder:
## Details
## Details
The example creates two LibP2P Hosts. Host1 opens a stream to Host2. Host2 has an `StreamHandler` to deal with the incoming stream. This is covered in the `echo` example.
The example creates two LibP2P Hosts supporting 2 protocols: ping and echo.
Each protocol consists RPC-style requests and respones and each request and response is a typed protobufs message (and a go data object).
This is a different pattern then defining a whole p2p protocol as 1 protobuf message with lots of optional fields (as can be observed in various p2p-lib protocols using protobufs such as dht).
The example shows how to match async received responses with their requests. This is useful when processing a response requires access to the request data.
Both hosts simulate a conversation. But rather than sending raw messages on the stream, each message in the conversation is encoded under a `json` object (using the `json` multicodec). For example:
The stream lasts until one of the sides closes it when the HangUp field is `true`.