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<ol class="chapter"><li class="chapter-item expanded affix "><a href="../index.html">Go语言圣经</a></li><li class="chapter-item expanded affix "><a href="../preface-zh.html">译者序</a></li><li class="chapter-item expanded affix "><a href="../preface.html">前言</a></li><li class="chapter-item expanded "><a href="../ch1/ch1.html"><strong aria-hidden="true">1.</strong> 入门</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../ch1/ch1-01.html"><strong aria-hidden="true">1.1.</strong> Hello, World</a></li><li class="chapter-item expanded "><a href="../ch1/ch1-02.html"><strong aria-hidden="true">1.2.</strong> 命令行参数</a></li><li class="chapter-item expanded "><a href="../ch1/ch1-03.html"><strong aria-hidden="true">1.3.</strong> 查找重复的行</a></li><li class="chapter-item expanded "><a href="../ch1/ch1-04.html"><strong aria-hidden="true">1.4.</strong> GIF动画</a></li><li class="chapter-item expanded "><a href="../ch1/ch1-05.html"><strong aria-hidden="true">1.5.</strong> 获取URL</a></li><li class="chapter-item expanded "><a href="../ch1/ch1-06.html"><strong aria-hidden="true">1.6.</strong> 并发获取多个URL</a></li><li class="chapter-item expanded "><a href="../ch1/ch1-07.html"><strong aria-hidden="true">1.7.</strong> Web服务</a></li><li class="chapter-item expanded "><a href="../ch1/ch1-08.html"><strong aria-hidden="true">1.8.</strong> 本章要点</a></li></ol></li><li class="chapter-item expanded "><a href="../ch2/ch2.html"><strong aria-hidden="true">2.</strong> 程序结构</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../ch2/ch2-01.html"><strong aria-hidden="true">2.1.</strong> 命名</a></li><li class="chapter-item expanded "><a href="../ch2/ch2-02.html"><strong aria-hidden="true">2.2.</strong> 声明</a></li><li class="chapter-item expanded "><a href="../ch2/ch2-03.html"><strong aria-hidden="true">2.3.</strong> 变量</a></li><li class="chapter-item expanded "><a href="../ch2/ch2-04.html"><strong aria-hidden="true">2.4.</strong> 赋值</a></li><li class="chapter-item expanded "><a href="../ch2/ch2-05.html"><strong aria-hidden="true">2.5.</strong> 类型</a></li><li class="chapter-item expanded "><a href="../ch2/ch2-06.html"><strong aria-hidden="true">2.6.</strong> 包和文件</a></li><li class="chapter-item expanded "><a href="../ch2/ch2-07.html"><strong aria-hidden="true">2.7.</strong> 作用域</a></li></ol></li><li class="chapter-item expanded "><a href="../ch3/ch3.html"><strong aria-hidden="true">3.</strong> 基础数据类型</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../ch3/ch3-01.html"><strong aria-hidden="true">3.1.</strong> 整型</a></li><li class="chapter-item expanded "><a href="../ch3/ch3-02.html"><strong aria-hidden="true">3.2.</strong> 浮点数</a></li><li class="chapter-item expanded "><a href="../ch3/ch3-03.html"><strong aria-hidden="true">3.3.</strong> 复数</a></li><li class="chapter-item expanded "><a href="../ch3/ch3-04.html"><strong aria-hidden="true">3.4.</strong> 布尔型</a></li><li class="chapter-item expanded "><a href="../ch3/ch3-05.html"><strong aria-hidden="true">3.5.</strong> 字符串</a></li><li class="chapter-item expanded "><a href="../ch3/ch3-06.html"><strong aria-hidden="true">3.6.</strong> 常量</a></li></ol></li><li class="chapter-item expanded "><a href="../ch4/ch4.html"><strong aria-hidden="true">4.</strong> 复合数据类型</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../ch4/ch4-01.html"><strong aria-hidden="true">4.1.</strong> 数组</a></li><li class="chapter-item expanded "><a href="../ch4/ch4-02.html"><strong aria-hidden="true">4.2.</strong> Slice</a></li><li class="chapter-item expanded "><a href="../ch4/ch4-03.html"><strong aria-hidden="true">4.3.</strong> Map</a></li><li class="chapter-item expanded "><a href="../ch4/ch4-04.html"><strong aria-hidden="true">4.4.</strong> 结构体</a></li><li class="chapter-item expanded "><a href="../ch4/ch4-05.html"><strong aria-hidden="true">4.5.</strong> JSON</a></li><li class="chapter-item expanded "><a href="../ch4/ch4-06.html"><strong aria-hidden="true">4.6.</strong> 文本和HTML模板</a></li></ol></li><li class="chapter-item expanded "><a href="../ch5/ch5.html"><strong aria-hidden="true">5.</strong> 函数</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../ch5/ch5-01.html"><strong aria-hidden="true">5.1.</strong> 函数声明</a></li><li class="chapter-item expanded "><a href="../ch5/ch5-02.html"><strong aria-hidden="true">5.2.</strong> 递归</a></li><li class="chapter-item expanded "><a href="../ch5/ch5-03.html"><strong aria-hidden="true">5.3.</strong> 多返回值</a></li><li class="chapter-item expanded "><a href="../ch5/ch5-04.html"><strong aria-hidden="true">5.4.</strong> 错误</a></li><li class="chapter-item expanded "><a href="../ch5/ch5-05.html"><strong aria-hidden="true">5.5.</strong> 函数值</a></li><li class="chapter-item expanded "><a href="../ch5/ch5-06.html"><strong aria-hidden="true">5.6.</strong> 匿名函数</a></li><li class="chapter-item expanded "><a href="../ch5/ch5-07.html"><strong aria-hidden="true">5.7.</strong> 可变参数</a></li><li class="chapter-item expanded "><a href="../ch5/ch5-08.html"><strong aria-hidden="true">5.8.</strong> Deferred函数</a></li><li class="chapter-item expanded "><a href="../ch5/ch5-09.html"><strong aria-hidden="true">5.9.</strong> Panic异常</a></li><li class="chapter-item expanded "><a href="../ch5/ch5-10.html"><strong aria-hidden="true">5.10.</strong> Recover捕获异常</a></li></ol></li><li class="chapter-item expanded "><a href="../ch6/ch6.html"><strong aria-hidden="true">6.</strong> 方法</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../ch6/ch6-01.html"><strong aria-hidden="true">6.1.</strong> 方法声明</a></li><li class="chapter-item expanded "><a href="../ch6/ch6-02.html"><strong aria-hidden="true">6.2.</strong> 基于指针对象的方法</a></li><li class="chapter-item expanded "><a href="../ch6/ch6-03.html"><strong aria-hidden="true">6.3.</strong> 通过嵌入结构体来扩展类型</a></li><li class="chapter-item expanded "><a href="../ch6/ch6-04.html"><strong aria-hidden="true">6.4.</strong> 方法值和方法表达式</a></li><li class="chapter-item expanded "><a href="../ch6/ch6-05.html"><strong aria-hidden="true">6.5.</strong> 示例: Bit数组</a></li><li class="chapter-item expanded "><a href="../ch6/ch6-06.html"><strong aria-hidden="true">6.6.</strong> 封装</a></li></ol></li><li class="chapter-item expanded "><a href="../ch7/ch7.html"><strong aria-hidden="true">7.</strong> 接口</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../ch7/ch7-01.html"><strong aria-hidden="true">7.1.</strong> 接口是合约</a></li><li class="chapter-item expanded "><a href="../ch7/ch7-02.html"><strong aria-hidden="true">7.2.</strong> 接口类型</a></li><li class="chapter-item expanded "><a href="../ch7/ch7-03.html"><strong aria-hidden="true">7.3.</strong> 实现接口的条件</a></li><li class="chapter-item expanded "><a href="../ch7/ch7-04.html"><strong aria-hidden="true">7.4.</strong> flag.Value接口</a></li><li class="chapter-item expanded "><a href="../ch7/ch7-05.html"><strong aria-hidden="true">7.5.</strong> 接口值</a></li><li class="chapter-item expanded "><a href="../ch7/ch7-06.html"><strong aria-hidden="true">7.6.</strong> sort.Interface接口</a></li><li class="chapter-item expanded "><a href="../ch7/ch7-07.html"><strong aria-hidden="true">7.7.</strong> http.Handler接口</a></li><li class="chapter-item expanded "><a href="../ch7/ch7-08.html"><strong aria-hidden="true">7.8.</strong> error接口</a></li><li class="chapter-item expanded "><a href="../ch7/ch7-09.html"><strong aria-hidden="true">7.9.</strong> 示例: 表达式求值</a></li><li class="chapter-item expanded "><a href="../ch7/ch7-10.html"><strong aria-hidden="true">7.10.</strong> 类型断言</a></li><li class="chapter-item expanded "><a href="../ch7/ch7-11.html"><strong aria-hidden="true">7.11.</strong> 基于类型断言识别错误类型</a></li><li class="chapter-item expanded "><a href="../ch7/ch7-12.html"><strong aria-hidden="true">7.12.</strong> 通过类型断言查询接口</a></li><li class="chapter-item expanded "><a href="../ch7/ch7-13.html"><strong aria-hidden="true">7.13.</strong> 类型分支</a></li><li class="chapter-item expanded "><a href="../ch7/ch7-14.html"><strong aria-hidden="true">7.14.</strong> 示例: 基于标记的XML解码</a></li><li class="chapter-item expanded "><a href="../ch7/ch7-15.html"><strong aria-hidden="true">7.15.</strong> 补充几点</a></li></ol></li><li class="chapter-item expanded "><a href="../ch8/ch8.html"><strong aria-hidden="true">8.</strong> Goroutines和Channels</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../ch8/ch8-01.html"><strong aria-hidden="true">8.1.</strong> Goroutines</a></li><li class="chapter-item expanded "><a href="../ch8/ch8-02.html" class="active"><strong aria-hidden="true">8.2.</strong> 示例: 并发的Clock服务</a></li><li class="chapter-item expanded "><a href="../ch8/ch8-03.html"><strong aria-hidden="true">8.3.</strong> 示例: 并发的Echo服务</a></li><li class="chapter-item expanded "><a href="../ch8/ch8-04.html"><strong aria-hidden="true">8.4.</strong> Channels</a></li><li class="chapter-item expanded "><a href="../ch8/ch8-05.html"><strong aria-hidden="true">8.5.</strong> 并发的循环</a></li><li class="chapter-item expanded "><a href="../ch8/ch8-06.html"><strong aria-hidden="true">8.6.</strong> 示例: 并发的Web爬虫</a></li><li class="chapter-item expanded "><a href="../ch8/ch8-07.html"><strong aria-hidden="true">8.7.</strong> 基于select的多路复用</a></li><li class="chapter-item expanded "><a href="../ch8/ch8-08.html"><strong aria-hidden="true">8.8.</strong> 示例: 并发的目录遍历</a></li><li class="chapter-item expanded "><a href="../ch8/ch8-09.html"><strong aria-hidden="true">8.9.</strong> 并发的退出</a></li><li class="chapter-item expanded "><a href="../ch8/ch8-10.html"><strong aria-hidden="true">8.10.</strong> 示例: 聊天服务</a></li></ol></li><li class="chapter-item expanded "><a href="../ch9/ch9.html"><strong aria-hidden="true">9.</strong> 基于共享变量的并发</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../ch9/ch9-01.html"><strong aria-hidden="true">9.1.</strong> 竞争条件</a></li><li class="chapter-item expanded "><a href="../ch9/ch9-02.html"><strong aria-hidden="true">9.2.</strong> sync.Mutex互斥锁</a></li><li class="chapter-item expanded "><a href="../ch9/ch9-03.html"><strong aria-hidden="true">9.3.</strong> sync.RWMutex读写锁</a></li><li class="chapter-item expanded "><a href="../ch9/ch9-04.html"><strong aria-hidden="true">9.4.</strong> 内存同步</a></li><li class="chapter-item expanded "><a href="../ch9/ch9-05.html"><strong aria-hidden="true">9.5.</strong> sync.Once惰性初始化</a></li><li class="chapter-item expanded "><a href="../ch9/ch9-06.html"><strong aria-hidden="true">9.6.</strong> 竞争条件检测</a></li><li class="chapter-item expanded "><a href="../ch9/ch9-07.html"><strong aria-hidden="true">9.7.</strong> 示例: 并发的非阻塞缓存</a></li><li class="chapter-item expanded "><a href="../ch9/ch9-08.html"><strong aria-hidden="true">9.8.</strong> Goroutines和线程</a></li></ol></li><li class="chapter-item expanded "><a href="../ch10/ch10.html"><strong aria-hidden="true">10.</strong> 包和工具</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../ch10/ch10-01.html"><strong aria-hidden="true">10.1.</strong> 包简介</a></li><li class="chapter-item expanded "><a href="../ch10/ch10-02.html"><strong aria-hidden="true">10.2.</strong> 导入路径</a></li><li class="chapter-item expanded "><a href="../ch10/ch10-03.html"><strong aria-hidden="true">10.3.</strong> 包声明</a></li><li class="chapter-item expanded "><a href="../ch10/ch10-04.html"><strong aria-hidden="true">10.4.</strong> 导入声明</a></li><li class="chapter-item expanded "><a href="../ch10/ch10-05.html"><strong aria-hidden="true">10.5.</strong> 包的匿名导入</a></li><li class="chapter-item expanded "><a href="../ch10/ch10-06.html"><strong aria-hidden="true">10.6.</strong> 包和命名</a></li><li class="chapter-item expanded "><a href="../ch10/ch10-07.html"><strong aria-hidden="true">10.7.</strong> 工具</a></li></ol></li><li class="chapter-item expanded "><a href="../ch11/ch11.html"><strong aria-hidden="true">11.</strong> 测试</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../ch11/ch11-01.html"><strong aria-hidden="true">11.1.</strong> go test</a></li><li class="chapter-item expanded "><a href="../ch11/ch11-02.html"><strong aria-hidden="true">11.2.</strong> 测试函数</a></li><li class="chapter-item expanded "><a href="../ch11/ch11-03.html"><strong aria-hidden="true">11.3.</strong> 测试覆盖率</a></li><li class="chapter-item expanded "><a href="../ch11/ch11-04.html"><strong aria-hidden="true">11.4.</strong> 基准测试</a></li><li class="chapter-item expanded "><a href="../ch11/ch11-05.html"><strong aria-hidden="true">11.5.</strong> 剖析</a></li><li class="chapter-item expanded "><a href="../ch11/ch11-06.html"><strong aria-hidden="true">11.6.</strong> 示例函数</a></li></ol></li><li class="chapter-item expanded "><a href="../ch12/ch12.html"><strong aria-hidden="true">12.</strong> 反射</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../ch12/ch12-01.html"><strong aria-hidden="true">12.1.</strong> 为何需要反射?</a></li><li class="chapter-item expanded "><a href="../ch12/ch12-02.html"><strong aria-hidden="true">12.2.</strong> reflect.Type和reflect.Value</a></li><li class="chapter-item expanded "><a href="../ch12/ch12-03.html"><strong aria-hidden="true">12.3.</strong> Display递归打印</a></li><li class="chapter-item expanded "><a href="../ch12/ch12-04.html"><strong aria-hidden="true">12.4.</strong> 示例: 编码S表达式</a></li><li class="chapter-item expanded "><a href="../ch12/ch12-05.html"><strong aria-hidden="true">12.5.</strong> 通过reflect.Value修改值</a></li><li class="chapter-item expanded "><a href="../ch12/ch12-06.html"><strong aria-hidden="true">12.6.</strong> 示例: 解码S表达式</a></li><li class="chapter-item expanded "><a href="../ch12/ch12-07.html"><strong aria-hidden="true">12.7.</strong> 获取结构体字段标签</a></li><li class="chapter-item expanded "><a href="../ch12/ch12-08.html"><strong aria-hidden="true">12.8.</strong> 显示一个类型的方法集</a></li><li class="chapter-item expanded "><a href="../ch12/ch12-09.html"><strong aria-hidden="true">12.9.</strong> 几点忠告</a></li></ol></li><li class="chapter-item expanded "><a href="../ch13/ch13.html"><strong aria-hidden="true">13.</strong> 底层编程</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../ch13/ch13-01.html"><strong aria-hidden="true">13.1.</strong> unsafe.Sizeof, Alignof 和 Offsetof</a></li><li class="chapter-item expanded "><a href="../ch13/ch13-02.html"><strong aria-hidden="true">13.2.</strong> unsafe.Pointer</a></li><li class="chapter-item expanded "><a href="../ch13/ch13-03.html"><strong aria-hidden="true">13.3.</strong> 示例: 深度相等判断</a></li><li class="chapter-item expanded "><a href="../ch13/ch13-04.html"><strong aria-hidden="true">13.4.</strong> 通过cgo调用C代码</a></li><li class="chapter-item expanded "><a href="../ch13/ch13-05.html"><strong aria-hidden="true">13.5.</strong> 几点忠告</a></li></ol></li><li class="chapter-item expanded "><a href="../appendix/appendix.html"><strong aria-hidden="true">14.</strong> 附录</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../appendix/appendix-a-errata.html"><strong aria-hidden="true">14.1.</strong> 附录A:原文勘误</a></li><li class="chapter-item expanded "><a href="../appendix/appendix-b-author.html"><strong aria-hidden="true">14.2.</strong> 附录B:作者译者</a></li><li class="chapter-item expanded "><a href="../appendix/appendix-c-cpoyright.html"><strong aria-hidden="true">14.3.</strong> 附录C:译文授权</a></li><li class="chapter-item expanded "><a href="../appendix/appendix-d-translations.html"><strong aria-hidden="true">14.4.</strong> 附录D:其它语言</a></li></ol></li></ol> </div>
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<main>
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<!-- 头部 -->
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<ul dir="auto">
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<li><em>Go语言圣经读书笔记(挖坑中...): <a href="https://github.com/chai2010/gopl-notes-zh">https://github.com/chai2010/gopl-notes-zh</a></em></li>
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<li><em>凹语言(Go实现, 面向WASM设计): <a href="https://github.com/wa-lang/wa">https://github.com/wa-lang/wa</a></em></li>
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</ul>
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<hr>
|
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|
||
<h2 id="82-示例-并发的clock服务"><a class="header" href="#82-示例-并发的clock服务">8.2. 示例: 并发的Clock服务</a></h2>
|
||
<p>网络编程是并发大显身手的一个领域,由于服务器是最典型的需要同时处理很多连接的程序,这些连接一般来自于彼此独立的客户端。在本小节中,我们会讲解go语言的net包,这个包提供编写一个网络客户端或者服务器程序的基本组件,无论两者间通信是使用TCP、UDP或者Unix domain sockets。在第一章中我们使用过的net/http包里的方法,也算是net包的一部分。</p>
|
||
<p>我们的第一个例子是一个顺序执行的时钟服务器,它会每隔一秒钟将当前时间写到客户端:</p>
|
||
<p><u><i>gopl.io/ch8/clock1</i></u></p>
|
||
<pre><code class="language-go">// Clock1 is a TCP server that periodically writes the time.
|
||
package main
|
||
|
||
import (
|
||
"io"
|
||
"log"
|
||
"net"
|
||
"time"
|
||
)
|
||
|
||
func main() {
|
||
listener, err := net.Listen("tcp", "localhost:8000")
|
||
if err != nil {
|
||
log.Fatal(err)
|
||
}
|
||
|
||
for {
|
||
conn, err := listener.Accept()
|
||
if err != nil {
|
||
log.Print(err) // e.g., connection aborted
|
||
continue
|
||
}
|
||
handleConn(conn) // handle one connection at a time
|
||
}
|
||
}
|
||
|
||
func handleConn(c net.Conn) {
|
||
defer c.Close()
|
||
for {
|
||
_, err := io.WriteString(c, time.Now().Format("15:04:05\n"))
|
||
if err != nil {
|
||
return // e.g., client disconnected
|
||
}
|
||
time.Sleep(1 * time.Second)
|
||
}
|
||
}
|
||
|
||
</code></pre>
|
||
<p>Listen函数创建了一个net.Listener的对象,这个对象会监听一个网络端口上到来的连接,在这个例子里我们用的是TCP的localhost:8000端口。listener对象的Accept方法会直接阻塞,直到一个新的连接被创建,然后会返回一个net.Conn对象来表示这个连接。</p>
|
||
<p>handleConn函数会处理一个完整的客户端连接。在一个for死循环中,用time.Now()获取当前时刻,然后写到客户端。由于net.Conn实现了io.Writer接口,我们可以直接向其写入内容。这个死循环会一直执行,直到写入失败。最可能的原因是客户端主动断开连接。这种情况下handleConn函数会用defer调用关闭服务器侧的连接,然后返回到主函数,继续等待下一个连接请求。</p>
|
||
<p>time.Time.Format方法提供了一种格式化日期和时间信息的方式。它的参数是一个格式化模板,标识如何来格式化时间,而这个格式化模板限定为Mon Jan 2 03:04:05PM 2006 UTC-0700。有8个部分(周几、月份、一个月的第几天……)。可以以任意的形式来组合前面这个模板;出现在模板中的部分会作为参考来对时间格式进行输出。在上面的例子中我们只用到了小时、分钟和秒。time包里定义了很多标准时间格式,比如time.RFC1123。在进行格式化的逆向操作time.Parse时,也会用到同样的策略。(译注:这是go语言和其它语言相比比较奇葩的一个地方。你需要记住格式化字符串是1月2日下午3点4分5秒零六年UTC-0700,而不像其它语言那样Y-m-d H:i:s一样,当然了这里可以用1234567的方式来记忆,倒是也不麻烦。)</p>
|
||
<p>为了连接例子里的服务器,我们需要一个客户端程序,比如netcat这个工具(nc命令),这个工具可以用来执行网络连接操作。</p>
|
||
<pre><code>$ go build gopl.io/ch8/clock1
|
||
$ ./clock1 &
|
||
$ nc localhost 8000
|
||
13:58:54
|
||
13:58:55
|
||
13:58:56
|
||
13:58:57
|
||
^C
|
||
</code></pre>
|
||
<p>客户端将服务器发来的时间显示了出来,我们用Control+C来中断客户端的执行,在Unix系统上,你会看到^C这样的响应。如果你的系统没有装nc这个工具,你可以用telnet来实现同样的效果,或者也可以用我们下面的这个用go写的简单的telnet程序,用net.Dial就可以简单地创建一个TCP连接:</p>
|
||
<p><u><i>gopl.io/ch8/netcat1</i></u></p>
|
||
<pre><code class="language-go">// Netcat1 is a read-only TCP client.
|
||
package main
|
||
|
||
import (
|
||
"io"
|
||
"log"
|
||
"net"
|
||
"os"
|
||
)
|
||
|
||
func main() {
|
||
conn, err := net.Dial("tcp", "localhost:8000")
|
||
if err != nil {
|
||
log.Fatal(err)
|
||
}
|
||
defer conn.Close()
|
||
mustCopy(os.Stdout, conn)
|
||
}
|
||
|
||
func mustCopy(dst io.Writer, src io.Reader) {
|
||
if _, err := io.Copy(dst, src); err != nil {
|
||
log.Fatal(err)
|
||
}
|
||
}
|
||
</code></pre>
|
||
<p>这个程序会从连接中读取数据,并将读到的内容写到标准输出中,直到遇到end of file的条件或者发生错误。mustCopy这个函数我们在本节的几个例子中都会用到。让我们同时运行两个客户端来进行一个测试,这里可以开两个终端窗口,下面左边的是其中的一个的输出,右边的是另一个的输出:</p>
|
||
<pre><code>$ go build gopl.io/ch8/netcat1
|
||
$ ./netcat1
|
||
13:58:54 $ ./netcat1
|
||
13:58:55
|
||
13:58:56
|
||
^C
|
||
13:58:57
|
||
13:58:58
|
||
13:58:59
|
||
^C
|
||
$ killall clock1
|
||
</code></pre>
|
||
<p>killall命令是一个Unix命令行工具,可以用给定的进程名来杀掉所有名字匹配的进程。</p>
|
||
<p>第二个客户端必须等待第一个客户端完成工作,这样服务端才能继续向后执行;因为我们这里的服务器程序同一时间只能处理一个客户端连接。我们这里对服务端程序做一点小改动,使其支持并发:在handleConn函数调用的地方增加go关键字,让每一次handleConn的调用都进入一个独立的goroutine。</p>
|
||
<p><u><i>gopl.io/ch8/clock2</i></u></p>
|
||
<pre><code class="language-go">for {
|
||
conn, err := listener.Accept()
|
||
if err != nil {
|
||
log.Print(err) // e.g., connection aborted
|
||
continue
|
||
}
|
||
go handleConn(conn) // handle connections concurrently
|
||
}
|
||
|
||
</code></pre>
|
||
<p>现在多个客户端可以同时接收到时间了:</p>
|
||
<pre><code>$ go build gopl.io/ch8/clock2
|
||
$ ./clock2 &
|
||
$ go build gopl.io/ch8/netcat1
|
||
$ ./netcat1
|
||
14:02:54 $ ./netcat1
|
||
14:02:55 14:02:55
|
||
14:02:56 14:02:56
|
||
14:02:57 ^C
|
||
14:02:58
|
||
14:02:59 $ ./netcat1
|
||
14:03:00 14:03:00
|
||
14:03:01 14:03:01
|
||
^C 14:03:02
|
||
^C
|
||
$ killall clock2
|
||
</code></pre>
|
||
<p><strong>练习 8.1:</strong> 修改clock2来支持传入参数作为端口号,然后写一个clockwall的程序,这个程序可以同时与多个clock服务器通信,从多个服务器中读取时间,并且在一个表格中一次显示所有服务器传回的结果,类似于你在某些办公室里看到的时钟墙。如果你有地理学上分布式的服务器可以用的话,让这些服务器跑在不同的机器上面;或者在同一台机器上跑多个不同的实例,这些实例监听不同的端口,假装自己在不同的时区。像下面这样:</p>
|
||
<pre><code>$ TZ=US/Eastern ./clock2 -port 8010 &
|
||
$ TZ=Asia/Tokyo ./clock2 -port 8020 &
|
||
$ TZ=Europe/London ./clock2 -port 8030 &
|
||
$ clockwall NewYork=localhost:8010 Tokyo=localhost:8020 London=localhost:8030
|
||
</code></pre>
|
||
<p><strong>练习 8.2:</strong> 实现一个并发FTP服务器。服务器应该解析客户端发来的一些命令,比如cd命令来切换目录,ls来列出目录内文件,get和send来传输文件,close来关闭连接。你可以用标准的ftp命令来作为客户端,或者也可以自己实现一个。</p>
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