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< h1 id = "构建单线程-web-服务器" > < a class = "header" href = "#构建单线程-web-服务器" > 构建单线程 Web 服务器< / a > < / h1 >
< p > 在开始之前先来简单回顾下构建所需的网络协议: HTTP 和 TCP。这两种协议都是请求-应答模式的网络协议，意味着在客户端发起请求后，服务器会监听并处理进入的请求，最后给予应答，至于这个过程怎么进行，取决于具体的协议定义。< / p >
< p > 与 HTTP 有所不同， TCP 是一个底层协议，它仅描述客户端传递了信息给服务器，至于这个信息长什么样，怎么解析处理，则不在该协议的职责范畴内。< / p >
< p > 而 HTTP 协议是更高层的通信协议，一般来说都基于 TCP 来构建 (HTTP/3 是基于 UDP 构建的协议)，更高层的协议也意味着它会对传输的信息进行解析处理。< / p >
< p > 更加深入的学习网络协议并不属于本书的范畴，因此让我们从如何读取 TCP 传输的字节流开始吧。< / p >
< h2 id = "监听-tcp-连接" > < a class = "header" href = "#监听-tcp-连接" > 监听 TCP 连接< / a > < / h2 >
< p > 先来创建一个全新的项目:< / p >
< pre > < code class = "language-shell" > $ cargo new hello
Created binary (application) `hello` project
$ cd hello
< / code > < / pre >
< p > 接下来，使用 < code > std::net< / code > 模块监听进入的请求连接， < code > 127.0.0.1:7878< / code > 。< / p >
< pre class = "playground" > < code class = "language-rust edition2021" > use std::net::TcpListener;
fn main() {
// 监听地址: 127.0.0.1:7878
let listener = TcpListener::bind("127.0.0.1:7878").unwrap();
for stream in listener.incoming() {
let stream = stream.unwrap();
println!("Connection established!");
}
}< / code > < / pre >
< p > 选择 < code > 7878< / code > 端口的原因是，< code > 80< / code > 和 < code > 8080< / code > 往往都被 HTTP 服务器霸占，因此我们需要选择一个跟已经监听的端口不冲突的。< / p >
< p > < code > bind< / code > 非常类似 < code > new< / code > ，它返回一个 < code > TcpListener< / code > 实例，只不过我们一般都说 “绑定到某个端口”，因此 < code > bind< / code > 这个名称会更合适。< / p >
< p > < code > unwrap< / code > 的使用是因为 < code > bind< / code > 返回 < code > Result< T,E> < / code > ，毕竟监听是有可能报错的，例如：如果要监听 < code > 80< / code > 端口往往需要管理员权限；监听了同样的端口，等等。< / p >
< p > < code > incoming< / code > 会返回一个迭代器，它每一次迭代都会返回一个新的连接 < code > stream< / code > (客户端发起， < code > stream< / code > 中读取数据，然后返回处理后的结果。< / p >
< p > 细心的同学可能会注意到，代码中对 < code > stream< / code > 还进行了一次 < code > unwrap< / code > 处理，原因在于我们并不是在迭代一个一个连接，而是在迭代处理一个一个请求建立连接的尝试，而这种尝试可能会失败！例如，操作系统的最大连接数限制。< / p >
< p > 现在，启动服务器，然后在你的浏览器中，访问地址 < code > 127.0.0.1:7878< / code > ，这时应该会看到一条错误信息，类似: “Connection reset”， ， < / p >
< pre > < code class = "language-shell" > $ cargo run
Running `target/debug/hello`
Connection established!
Connection established!
Connection established!
< / code > < / pre >
< p > 无论浏览器怎么摆烂， ： < / p >
< p > 可能大家会疑问，为啥在浏览器访问一次，可能会在终端打印出多次请求建立的信息，难道不是应该一一对应吗？原因在于当 < code > stream< / code > 超出作用域时，会触发 < code > drop< / code > 的扫尾工作，其中包含了关闭连接。但是，浏览器可能会存在自动重试的情况，因此还会重新建立连接，最终打印了多次。< / p >
< p > 由于 < code > listener.incoming< / code > 会在当前阻塞式监听，也就是 < code > main< / code > 线程会被阻塞，我们最后需要通过 < code > ctrl + c< / code > 来结束程序进程。< / p >
< h2 id = "读取请求" > < a class = "header" href = "#读取请求" > 读取请求< / a > < / h2 >
< p > 连接建立后，就可以开始读取客户端传来的数据:< / p >
< pre class = "playground" > < code class = "language-rust edition2021" > use std::{
io::{prelude::*, BufReader},
net::{TcpListener, TcpStream},
};
fn main() {
let listener = TcpListener::bind("127.0.0.1:7878").unwrap();
for stream in listener.incoming() {
let stream = stream.unwrap();
handle_connection(stream);
}
}
fn handle_connection(mut stream: TcpStream) {
let buf_reader = BufReader::new(& mut stream);
let http_request: Vec< _> = buf_reader
.lines()
.map(|result| result.unwrap())
.take_while(|line| !line.is_empty())
.collect();
println!("Request: {:#?}", http_request);
}< / code > < / pre >
< p > 这段代码有几点值得注意:< / p >
< ul >
< li > 引入 < code > std::io::prelude< / code > 和 < code > std::io::BufReader< / code > 是引入相应的特征和类型，帮助我们读取和写入数据< / li >
< li > < code > BufReader< / code > 可以实现缓冲区读取，底层其实是基于 < code > std::io::Read< / code > 实现< / li >
< li > 可以使用 < code > lines< / code > 方法来获取一个迭代器，可以对传输的内容流进行按行迭代读取，要使用该方法，必须先引入 < code > std::io::BufRead< / code > < / li >
< li > 最后使用 < code > collect< / code > 消费掉迭代器，最终客户端发来的请求数据被存到 < code > http_request< / code > 这个动态数组中< / li >
< / ul >
< p > 大家可能会比较好奇，该如何判断客户端发来的 HTTP 数据是否读取完成，答案就在于客户端会在请求数据的结尾附上两个换行符，当我们检测到某一行字符串为空时，就意味着请求数据已经传输完毕，可以 < code > collect< / code > 了。< / p >
< p > 来运行下试试:< / p >
< pre > < code class = "language-shell" > $ cargo run
Compiling hello v0.1.0 (file:///projects/hello)
Finished dev [unoptimized + debuginfo] target(s) in 0.42s
Running `target/debug/hello`
Request: [
"GET / HTTP/1.1",
"Host: 127.0.0.1:7878",
"User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:99.0) Gecko/20100101 Firefox/99.0",
"Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8",
"Accept-Language: en-US,en;q=0.5",
"Accept-Encoding: gzip, deflate, br",
"DNT: 1",
"Connection: keep-alive",
"Upgrade-Insecure-Requests: 1",
"Sec-Fetch-Dest: document",
"Sec-Fetch-Mode: navigate",
"Sec-Fetch-Site: none",
"Sec-Fetch-User: ?1",
"Cache-Control: max-age=0",
]
< / code > < / pre >
< p > 呦，还挺长的，是不是长得很像我们以前见过的 HTTP 请求 JSON， < / p >
< h2 id = "http-请求长啥样" > < a class = "header" href = "#http-请求长啥样" > HTTP 请求长啥样< / a > < / h2 >
< p > 刚才的文本挺长的，但其实符合以下的格式:< / p >
< pre > < code class = "language-text" > Method Request-URI HTTP-Version
headers CRLF
message-body
< / code > < / pre >
< ul >
< li > 第一行 Method 是请求的方法，例如 < code > GET< / code > 、< code > POST< / code > 等， < code > /< / code > 、< code > /hello/world< / code > 等< / li >
< li > 类似 JSON 格式的数据都是 HTTP 请求报头 headers， < code > "Host: 127.0.0.1:7878"< / code > < / li >
< li > 至于 message-body 是消息体， 它包含了用户请求携带的具体数据，例如更改用户名的请求，就要提交新的用户名数据，至于刚才的 < code > GET< / code > 请求，它是没有 message-body 的< / li >
< / ul >
< p > 大家可以尝试换一个浏览器再访问一次，看看不同的浏览器请求携带的 headers 是否不同。< / p >
< h2 id = "请求应答" > < a class = "header" href = "#请求应答" > 请求应答< / a > < / h2 >
< p > 目前为止， ， ， ， < / p >
< pre > < code class = "language-text" > HTTP-Version Status-Code Reason-Phrase CRLF
headers CRLF
message-body
< / code > < / pre >
< p > 应答的格式与请求相差不大，其中 Status-Code 是最重要的，它用于告诉客户端，当前的请求是否成功，若失败，大概是什么原因，它就是著名的 HTTP 状态码，常用的有 < code > 200< / code > : 请求成功，< code > 404< / code > 目标不存在，等等。< / p >
< p > 为了帮助大家更直观的感受下应答格式第一行长什么样，下面给出一个示例:< / p >
< pre > < code class = "language-text" > HTTP/1.1 200 OK\r\n\r\n
< / code > < / pre >
< p > 下面将该应答发送回客户端:< / p >
< pre class = "playground" > < code class = "language-rust edition2021" > < span class = "boring" > #![allow(unused)]
< / span > < span class = "boring" > fn main() {
< / span > fn handle_connection(mut stream: TcpStream) {
let buf_reader = BufReader::new(& mut stream);
let http_request: Vec< _> = buf_reader
.lines()
.map(|result| result.unwrap())
.take_while(|line| !line.is_empty())
.collect();
let response = "HTTP/1.1 200 OK\r\n\r\n";
stream.write_all(response.as_bytes()).unwrap();
}
< span class = "boring" > }< / span > < / code > < / pre >
< p > 由于 < code > write_all< / code > 方法接受 < code > & [u8]< / code > 类型作为参数，这里需要用 < code > as_bytes< / code > 将字符串转换为字节数组。< / p >
< p > 重新启动服务器，然后再观察下浏览器中的输出，这次应该不再有报错，而是一个空白页面，因为没有返回任何具体的数据( message-body )，上面只是一条最简单的符合 HTTP 格式的数据。< / p >
< h2 id = "返回-html-页面" > < a class = "header" href = "#返回-html-页面" > 返回 HTML 页面< / a > < / h2 >
< p > 空白页面显然会让人不知所措，那就返回一个简单的 HTML 页面，给用户打给招呼。< / p >
< p > 在项目的根目录下创建 < code > hello.html< / code > 文件并写入如下内容：< / p >
< pre > < code class = "language-html" > < !DOCTYPE html>
< html lang="en">
< head>
< meta charset="utf-8">
< title> Hello!< /title>
< /head>
< body>
< h1> Hello!< /h1>
< p> Hi from Rust< /p>
< /body>
< /html>
< / code > < / pre >
< p > 看得出来，这是一个非常简单的 HTML5 网页文档，基本上没人读不懂吧 ： ） < / p >
< pre class = "playground" > < code class = "language-rust edition2021" > < span class = "boring" > #![allow(unused)]
< / span > < span class = "boring" > fn main() {
< / span > use std::{
fs,
io::{prelude::*, BufReader},
net::{TcpListener, TcpStream},
};
// --snip--
fn handle_connection(mut stream: TcpStream) {
let buf_reader = BufReader::new(& mut stream);
let http_request: Vec< _> = buf_reader
.lines()
.map(|result| result.unwrap())
.take_while(|line| !line.is_empty())
.collect();
let status_line = "HTTP/1.1 200 OK";
let contents = fs::read_to_string("hello.html").unwrap();
let length = contents.len();
let response =
format!("{status_line}\r\nContent-Length: {length}\r\n\r\n{contents}");
stream.write_all(response.as_bytes()).unwrap();
}
< span class = "boring" > }< / span > < / code > < / pre >
< p > 新修改的代码中，读取了新增 HTML 的内容，并按照 HTTP 格式，将内容传回给客户端。< / p >
< p > 具体的运行验证就不再赘述，我们再来看看如何增加一些验证和选择性回复。< / p >
< blockquote >
< p > 用这么奇怪的格式返回应答数据，原因只有一个，我们在模拟实现真正的 http web 服务器框架。事实上，写逻辑代码时，只需使用现成的 web 框架( 例如 < a href = "https://rocket.rs" > < code > rocket< / code > < / a > )去启动 web 服务即可，解析请求数据和返回应答数据都已经被封装在 API 中，非常简单易用< / p >
< / blockquote >
< h2 id = "验证请求和选择性应答" > < a class = "header" href = "#验证请求和选择性应答" > 验证请求和选择性应答< / a > < / h2 >
< p > 用户想要获取他的个人信息，你给他 say hi， ， < / p >
< p > 是的，这种服务态度我们很欣赏，但是这种服务质量属实令人堪忧。因此我们要针对用户的不同请求给出相应的不同回复，让场景模拟更加真实。< / p >
< pre class = "playground" > < code class = "language-rust edition2021" > < span class = "boring" > #![allow(unused)]
< / span > < span class = "boring" > fn main() {
< / span > fn handle_connection(mut stream: TcpStream) {
let buf_reader = BufReader::new(& mut stream);
let request_line = buf_reader.lines().next().unwrap().unwrap();
if request_line == "GET / HTTP/1.1" {
let status_line = "HTTP/1.1 200 OK";
let contents = fs::read_to_string("hello.html").unwrap();
let length = contents.len();
let response = format!(
"{status_line}\r\nContent-Length: {length}\r\n\r\n{contents}"
);
stream.write_all(response.as_bytes()).unwrap();
} else {
// some other request
}
}
< span class = "boring" > }< / span > < / code > < / pre >
< p > 注意迭代器方法 < code > next< / code > 的使用，原因在于我们只需要读取第一行，判断具体的 HTTP METHOD 是什么。< / p >
< p > 接着判断了用户是否请求了 < code > /< / code > 根路径，如果是，返回之前的 < code > hello.html< / code > 页面；如果不是…尚未实现。< / p >
< p > 重新运行服务器，如果你继续访问 < code > 127.0.0.1:7878< / code > ，那么看到的依然是 < code > hello.html< / code > 页面，因为默认访问根路径，但是一旦换一个路径访问，例如 < code > 127.0.0.1:7878/something-else< / code > ，那你将继续看到之前看过多次的连接错误。< / p >
< p > 下面来完善下，当用户访问根路径之外的页面时，给他展示一个友好的 404 页面( 相比直接报错 )。< / p >
< pre class = "playground" > < code class = "language-rust edition2021" > < span class = "boring" > #![allow(unused)]
< / span > < span class = "boring" > fn main() {
< / span > // --snip--
} else {
let status_line = "HTTP/1.1 404 NOT FOUND";
let contents = fs::read_to_string("404.html").unwrap();
let length = contents.len();
let response = format!(
"{status_line}\r\nContent-Length: {length}\r\n\r\n{contents}"
);
stream.write_all(response.as_bytes()).unwrap();
}
< span class = "boring" > }< / span > < / code > < / pre >
< p > 哦对了，别忘了在根路径下创建 < code > 404.html< / code > 并填入下面内容:< / p >
< pre > < code class = "language-html" > < !DOCTYPE html>
< html lang="en">
< head>
< meta charset="utf-8">
< title> 你好!< /title>
< /head>
< body>
< h1> 很抱歉!< /h1>
< p> 由于运维删库跑路， ， ， < /p>
< /body>
< /html>
< / code > < / pre >
< p > 最后，上面的代码其实有很多重复，可以提取出来进行简单重构:< / p >
< pre class = "playground" > < code class = "language-rust edition2021" > < span class = "boring" > #![allow(unused)]
< / span > < span class = "boring" > fn main() {
< / span > // --snip--
fn handle_connection(mut stream: TcpStream) {
// --snip--
let (status_line, filename) = if request_line == "GET / HTTP/1.1" {
("HTTP/1.1 200 OK", "hello.html")
} else {
("HTTP/1.1 404 NOT FOUND", "404.html")
};
let contents = fs::read_to_string(filename).unwrap();
let length = contents.len();
let response =
format!("{status_line}\r\nContent-Length: {length}\r\n\r\n{contents}");
stream.write_all(response.as_bytes()).unwrap();
}
< span class = "boring" > }< / span > < / code > < / pre >
< p > 至此，单线程版本的服务器已经完成，但是说实话，没啥用，总不能让你的用户排队等待访问吧，那也太糟糕了…< / p >
< / main >
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< script src = "../elasticlunr-ef4e11c1.min.js" > < / script >
< script src = "../mark-09e88c2c.min.js" > < / script >
< script src = "../searcher-c2a407aa.js" > < / script >
< script src = "../clipboard-1626706a.min.js" > < / script >
< script src = "../highlight-abc7f01d.js" > < / script >
< script src = "../book-a0b12cfe.js" > < / script >
<!-- Custom JS scripts -->
< script src = "../assets/custom-7d8ae1df.js" > < / script >
< script src = "../assets/bigPicture-be03f9c8.js" > < / script >
< / div >
< / body >
< / html >
