摘要：發(fā)送響應頭信息參數用于指定一個三位的狀態(tài)碼參數值為一個字符串，用于指定對該狀態(tài)碼的描述信息為一個對象，用于指定服務器端創(chuàng)建的響應頭對象用于指定內容類型用于將客戶端重定向到另一個地址用于指定一個被下載的文件名用于指定服務器端響應內容的編

response.writeHead(statusCode, [reasonPhrase], [headers])

statusCode:參數用于指定一個三位的HTTP狀態(tài)碼

reasonPhrase:參數值為一個字符串，用于指定對該狀態(tài)碼的描述信息

headers:為一個對象，用于指定服務器端創(chuàng)建的響應頭對象

content-type:用于指定內容類型

location:用于將客戶端重定向到另一個url地址

content-disposition:用于指定一個被下載的文件名

content-length:用于指定服務器端響應內容的編碼格式

set-cookie:用于在客戶端創(chuàng)建一個cookie

content-encoding:用于指定服務器端響應內容的編碼方式

Cache-Control:用于開啟緩存機制

Expires:用于指定緩存過期時間

Etag:用于指定當服務器端響應內容沒有變化時不重新下載數據

多帶帶設置響應頭信息

可以使用http.ServerResponse對象的setHeader方法多帶帶設置響應頭信息。

* `response.setHeader(name, value)`
* `res.setHeader("Content-Type", "text/type");`

獲取響應頭某個字段的值

response.getHeader(name);

res.getHeader("Content-Type");

刪除一個響應字段

response.removeHeader(name);

res.removeHeader("Content-Type");

檢測響應頭是否已經發(fā)送

response.headersSent();

已發(fā)出，為true

未發(fā)送，為false

Date字段

默認情況下HTTP服務器會自動將服務器端當前時間作為響應頭中的Date字段值發(fā)送給客戶端，可以通過將res.sendDate屬性值設置為false的方法，在響應頭中刪除Date字段

res.sendDate = false;

簡單的HTTP服務器

const http = require("http");
let server = http.createServer(function (req, res) {
    if (req.url !== "/favicon.ico") {
        res.write("");
        res.sendDate = false; // 不發(fā)送時間
        if (res.headersSent) {
            console.log("第一個響應頭已經發(fā)送");
        } else {
            console.log("第一個響應頭未發(fā)送");
        }
        res.writeHead(200, {"Content-Type": "text/html"});
        if (res.headersSent) {
            console.log("第二個響應頭已經發(fā)送");
        } else {
            console.log("第二個響應頭未發(fā)送");
        }
        res.write("hello, this is http server response content");
    }
    res.end();
}).listen(2596, "localhost", function () {
    console.log("the http server is running at localhost:3333")
});

響應數據的尾部追加一個頭信息

res.addTrailers(headers)

const http = require("http");
let server = http.createServer(function (req, res) {
    if (req.url !== "/favicon.ico") {
        res.writeHead(200, {"Content-Type": "text/plain", "Trailer": "Content-MD5"});
        res.addTrailers({"Content-MD5": "5Q8W9XS5AS98ZX2X5V8V3ZX3ZA8"});
        res.write("hello, these are some new massage");
    }
    res.end();
}).listen(3333, "localhost", function () {
    console.log("the http server is running at localhost:3333")
});

const http = require("http");
const fs = require("fs");
const PORT = 2596;
let server = http.createServer((req, res) => {
    if (req.url !== "/favicon.ico") {
        let out = fs.createWriteStream("./requestCurl.log");
        out.write("客戶端請求的方法為:" + req.method + "
");
        out.write("客戶端請求的url字符串為:" + req.url + "
");
        out.write("客戶端請求頭對象為:" + JSON.stringify(req.headers) + "
");
        out.write("客戶端請求所用的HTTP版本為:" + req.httpVersion + "
");
        req.on("data", function (data) {
            console.log("服務器端接收到數據:" + data);
        });
        req.on("end", () => {
            console.log("客戶端請求數據已全部接收完畢");
        })
    }
    res.end();
}).listen(PORT, "localhost");

server.on("listening", () => {
    console.log(`server start listen localhost:${PORT}`);
});

server.on("connection", (socket) => {
    console.log("client and server had been connected");
});

setTimeout(10 * 1000, (socket) => {
    console.log("server response timeout");
});

server.on("error", (err) => {
    if (e.code === "EADDRINUSE") {
        console.log("the port has been used,please change your server port");
    }
    server.on("close", () => {
        console.log("server closed");
    });
});
/***
 * 客戶端請求的方法為:GET
 * 客戶端請求的url字符串為:/
 * 客戶端請求頭對象為:{"user-agent":"curl/7.29.0","host":"localhost:2596","accept":"*|*"}
 * 客戶端請求所用的HTTP版本為:1.1
 * */

當客戶端請求獲取到服務器響應流時，觸發(fā)res.on("data", (chunk) => {})事件

const http = require("http");
let options = {
    hostname: "www.qq.com",
    port: 80,
    path: "/",
    method: "GET"
};
let req = http.request(options, (res) => {
    console.log(`狀態(tài)碼：${res.statusCode}`);
    console.log(`響應頭：${JSON.stringify(res.headers)}`);
    res.setEncoding("utf8");
    res.on("data", (chunk) => {
        console.log(`響應內容：`);
    })
});
req.on("response", (res) => {
    console.log(res); // IncomingMessage
});
req.on("error", (err) => {
    if (err.code === "ECONNRESET") {
        console.log("socket端口超時");
    } else {
        console.log("在請求數據過程中發(fā)生錯誤，錯誤代碼為：" + err.code)
    }
});

req.end();
/**
* 狀態(tài)碼：200
* 響應頭：{
*     "server": "squid/3.5.24",
*     "date": "Sun, 25 Feb 2018 14:09:11 GMT",
*     "content-type": "text/html; charset=GB2312",
*     "transfer-encoding": "chunked",
*     "connection": "close",
*     "vary": "Accept-Encoding, Accept-Encoding, Accept-Encoding, Accept-Encoding",
*     "expires": "Sun, 25 Feb 2018 14:10:11 GMT",
*     "cache-control": "max-age=60",
*     "x-cache": "HIT from shenzhen.qq.com"
* }
* 
* **/