Unify serde transports.

This PR obsoletes the JSON and Bincode transports and instead introduces a unified transport that
is generic over any tokio-serde serialization format as well as AsyncRead + AsyncWrite medium.
This comes with a slight hit for usability (having to manually specify the underlying transport
and codec), but it can be alleviated by making custom freestanding connect and listen fns.

example-service/Cargo.toml

@@ -18,6 +18,7 @@ futures = "0.3"
 serde = { version = "1.0" }
 tarpc = { version = "0.18", path = "../tarpc", features = ["full"] }
 tokio = "0.2"
+tokio-serde = { version = "0.6", features = ["json"] }
 env_logger = "0.6"
 
 [lib]

example-service/src/client.rs

@@ -7,6 +7,7 @@
 use clap::{App, Arg};
 use std::{io, net::SocketAddr};
 use tarpc::{client, context};
+use tokio_serde::formats::Json;
 
 #[tokio::main]
 async fn main() -> io::Result<()> {
@@ -40,7 +41,7 @@ async fn main() -> io::Result<()> {
 
     let name = flags.value_of("name").unwrap().into();
 
-    let transport = tarpc::json_transport::connect(server_addr).await?;
+    let transport = tarpc::serde_transport::tcp::connect(server_addr, Json::default()).await?;
 
     // WorldClient is generated by the service attribute. It has a constructor `new` that takes a
     // config and any Transport as input.

example-service/src/server.rs

@@ -18,6 +18,7 @@ use tarpc::{
     context,
     server::{self, Channel, Handler},
 };
+use tokio_serde::formats::Json;
 
 // This is the type that implements the generated World trait. It is the business logic
 // and is used to start the server.
@@ -66,7 +67,7 @@ async fn main() -> io::Result<()> {
 
     // JSON transport is provided by the json_transport tarpc module. It makes it easy
     // to start up a serde-powered json serialization strategy over TCP.
-    tarpc::json_transport::listen(&server_addr)
+    tarpc::serde_transport::tcp::listen(&server_addr, Json::default)
         .await?
         // Ignore accept errors.
         .filter_map(|r| future::ready(r.ok()))