本文原版本為官方英文文檔，詳情見官方http://tokio.rs
網絡程序一般分為以下幾個層次:
Byte streams 層，處在最低層。這一層一般是提供TCP或者UDP Socket.這一層，一般操作byte buffer.TLS使用也是處在這一層。
Framing?is taking a raw stream of bytes and breaking it up into meaningful units. For example, HTTP naturally has frames consisting of request headers, response headers, or body chunks. A line-based protocol consists of String frames that are delineated by new line tokens. At this point, instead of dealing with a stream of raw bytes, we are dealing with a stream of frame values. In Tokio, we sometimes refer to a full duplex stream of frames as a?transport, which implements both the Stream and Sink traits.
Framing將一個原始的字節流，并分解成有意義的單位。例如，HTTP由請求頭，響應頭或主體塊組成的幀。基于行的協議由換行標記描述的字符串frame組成。在這一點上，我們不是處理一個原始字節流，而是處理一系列的frame值。在Tokio中，我們有時將幀的全雙工流稱為transport，它實現了Stream和Sink特性。
A?request / response exchange?generally is where application logic starts appearing. For a client, at this layer, a request is issued and a response for the request is returned. When the request is issued, it is turned into one or more frames and written to a transport. Then, at some point in the future, a response to the request will be read from the transport, and matched with the original request.
Request / Response應答層，一般是程序邏輯開始的地方。對于一個客戶端，這一層，一個請求發出時，他會轉換成一個或多個Frames，寫入Transport。然后，從這個Transport中讀取匹配原來請求的響應
At the?application?layer, the details of how requests and responses are mapped onto a transport don’t matter. A single application may be receiving and issuing requests for many different protocols. An HTTP server application will be receiving HTTP requests, and then in turn, issuing database requests or other HTTP requests.
應用層，不關心請求與響應如何映射到一個Transport中。一個應用程序也許通過許多不同的協議接收和發起請求。一個Http server應用程序會接收Http請求，然后發起數據庫請求或其它http請求。
Each of these layers tend to be implemented in different libraries, and the end application will pull in the protocol implementations and just interact with them at the request / response exchange layer.
每一層都是在不同的庫中實現的，最后，應用會將他們整合到協議實現中去，并在request / response應答中使用他們。
Tokio’s abstractions map onto these different layers.
Tokio對上述這些層進行一一抽象。
tokio-coreprovides the lowest level building blocks for writing asynchronous I/O code: anevent loopand theconcrete I/O types, such as TCP and UDP sockets. These primitives work on the byte level much like thestd::iotypes, except the Tokio types are non-blocking. Other sections describe bothhigh-levelandlow-levelAPIs for working with byte streams.
tokio-core提供最低層異步I/O代碼：event loop和具體的I/O類型，如TCP和UDP。主要工作中byte層，類似于std::IO類型，但是Tokio類型都是非阻塞的。其它部分都是描述上層和低層的處理byte Stream的api。
Framing is done with Tokio by first defining a frame type, usually an enum, then implementing a transport as aStream + Sinkthat works with that frame type. The transport handles encoding and decoding the frame values to the raw stream of bytes. This can either be donemanuallyor using a helper likeframed.
Framing Tokio首先定義一個Frame類型，通常是一個枚舉，然后實現了一個transport，實現Stream和Sink trait來處理這個Frame類型。Transport解碼和編碼這Frame值為byte stream.可以動手實現也可以使用framed helper.
Later sections coverworking with transportsandhandshakes in particular.
The request / response exchange layer is handled by Tokio’sServicetrait. TheServicetrait is a simplified interface making it easy to write network applications in a modular and reusable way, decoupled from the underlying protocol. It is one of Tokio’s fundamental abstractions. It is a similar abstraction to Finagle’sService, Ruby’s Rack, or Java’s servlet; however, Tokio’sServicetrait is abstract over the underlying protocol.
請求和應答層在Service trait中被處理。Service trait是一個簡單的接口，非常容易以模塊化和可重用的方式實現網絡應用層，與底層的協議解耦。這是Tokio基礎抽象之一，處在低層協議之上，類似于Finagle Service, Ruby Rack, Java servlet。
There are generally two ways to map request / responses to a stream of frames: pipelined ormultiplexing.tokio-proto’s goal is to take a transport and handle the required logic to map that to an implementation ofService.
通常有兩種方式將request / responses映射到一個幀流：pipelined或者multiplexing。tokio-proto的目標是將transport和處理所需的邏輯映射到一個服務實現。
A big advantage of having a standardizedServiceinterface is that it makes it possible to write reusable middleware components that add useful functionality.
標準的Service接口最大的優點是，可以寫可重用的中間層組件。
Generally, all the previously listed layers will be implemented in libraries. For example, an HTTP server implementation would implement an HTTP transport, then usetokio-prototo map that to aService. TheServiceis what the HTTP library would expose.
一般來說，所有之前列出的層都是在庫中實現的。例如一個http服務實現在一個http transport中，然后使用tokio-proto將其轉換成一個服務。
An application would depend on many different libraries, providing various protocol implementations exposed as services, and using thefutureslibrary to hook everything together.
一個應用依賴很多不同的庫，提供各種協議。作為服務提供出來，使用futures庫將所有東西結合在一起。
