242 CHAPTER 22. 网络和流 22.5 一个简单的 TCP 示例 让我们直接进入一个 TCP 套接字相关的简单示例。此功能位于名为 Sockets 的标准库中。让我们先 创建一个简单的服务器： julia> using Sockets julia> @async begin server = listen(2000) while true sock = accept(server) @0x00007fd31dc11ae0 对于那些熟悉 Unix 套接字 API 的人，这些方法名称会让人感觉很熟悉，可是它们的用法比原始的 Unix 套接字 API 要简单些。在本例中，首次调用 listen 会创建一个服务器，等待传入指定端口（2000）的 连接。 julia> listen(2000) # 监听（IPv4 下的）localhost:2000 Sockets.TCPServer(active) julia> 时，我们连接到刚刚创建的服务器。与此同时，accept 函数返回到新创建的套接字的服务 器端连接，并打印「Hello World」来表明连接成功。 Julia 的强大优势在于，即使 I/O 实际上是异步发生的，API 也以同步方式暴露，我们不必担心回调， 甚至不必确保服务器能够运行。在我们调用 connect 时，当前任务等待建立连接，并在这之后才继 续执行。在此暂停中，服务器任务恢复执行（因为现在

100%|████████████████████████████████| Time: 0:00:00 Main binary filename not available. Serving web UI on http://localhost:62261 "alloc-profile.pb.gz" Then you can view the profile by navigating to documentation. – Interfaces for Julia packages are typically described using docstrings, README.md, static web pages, ... • Some developers choose not to export all symbols required to use their package/module Julia is running in a JavaScript VM (JSVM), including e.g. a WebAssembly JavaScript embedding in a web browser. Julia 1.2 This function requires at least Julia 1.2. source Base.Sys.loadavg – Function

100%|████████████████████████████████| Time: 0:00:00 Main binary filename not available. Serving web UI on http://localhost:62261 "alloc-profile.pb.gz" Then you can view the profile by navigating to documentation. – Interfaces for Julia packages are typically described using docstrings, README.md, static web pages, ... • Some developers choose not to export all symbols required to use their package/module Julia is running in a JavaScript VM (JSVM), including e.g. a WebAssembly JavaScript embedding in a web browser. Julia 1.2 This function requires at least Julia 1.2. source Base.Sys.loadavg – Function

100%|████████████████████████████████| Time: 0:00:00 Main binary filename not available. Serving web UI on http://localhost:62261 "alloc-profile.pb.gz" Then you can view the profile by navigating to documentation. – Interfaces for Julia packages are typically described using docstrings, README.md, static web pages, ... • Some developers choose not to export all symbols required to use their package/module Julia is running in a JavaScript VM (JSVM), including e.g. a WebAssembly JavaScript embedding in a web browser. Julia 1.2 This function requires at least Julia 1.2. source Base.Sys.loadavg – Function

documentation. – Interfaces for Julia packages are typically described using docstrings, README.md, static web pages, ... • Some developers choose not to export all symbols required to use their package/module Julia is running in a JavaScript VM (JSVM), including e.g. a WebAssembly JavaScript embedding in a web browser. Julia 1.2 This function requires at least Julia 1.2. source Base.Sys.loadavg – Function 1113 49.1 Example In the example below we use a scoped value to implement a permission check in a web-application. After determining the permissions of the request, a new dynamic scope is entered and

documentation. – Interfaces for Julia packages are typically described using docstrings, README.md, static web pages, ... • Some developers choose not to export all symbols required to use their package/module Julia is running in a JavaScript VM (JSVM), including e.g. a WebAssembly JavaScript embedding in a web browser. Julia 1.2 This function requires at least Julia 1.2. source Base.Sys.loadavg – Function 1107 49.1 Example In the example below we use a scoped value to implement a permission check in a web-application. After determining the permissions of the request, a new dynamic scope is entered and

documentation. – Interfaces for Julia packages are typically described using docstrings, README.md, static web pages, ... • Some developers choose not to export all symbols required to use their package/module Julia is running in a JavaScript VM (JSVM), including e.g. a WebAssembly JavaScript embedding in a web browser. Julia 1.2 This function requires at least Julia 1.2. source Base.Sys.loadavg – Function end 49.1 Example In the example below we use a scoped value to implement a permission check in a web-application. After determining the permissions of the request, a new dynamic scope is entered and

100%|████████████████████████████████| Time: 0:00:00 Main binary filename not available. Serving web UI on http://localhost:62261 "alloc-profile.pb.gz" Then you can view the profile by navigating to documentation. – Interfaces for Julia packages are typically described using docstrings, README.md, static web pages, ... • Some developers choose not to export all symbols required to use their package/module Julia is running in a JavaScript VM (JSVM), including e.g. a WebAssembly JavaScript embedding in a web browser. Julia 1.2 This function requires at least Julia 1.2. source Base.Sys.loadavg – Function

100%|████████████████████████████████| Time: 0:00:00 Main binary filename not available. Serving web UI on http://localhost:62261 "alloc-profile.pb.gz" Then you can view the profile by navigating to documentation. – Interfaces for Julia packages are typically described using docstrings, README.md, static web pages, ... • Some developers choose not to export all symbols required to use their package/module Julia is running in a JavaScript VM (JSVM), including e.g. a WebAssembly JavaScript embedding in a web browser. Julia 1.2 This function requires at least Julia 1.2. source Base.Sys.loadavg – Function

100%|████████████████████████████████| Time: 0:00:00 Main binary filename not available. Serving web UI on http://localhost:62261 "alloc-profile.pb.gz" Then you can view the profile by navigating to documentation. – Interfaces for Julia packages are typically described using docstrings, README.md, static web pages, ... • Some developers choose not to export all symbols required to use their package/module Julia is running in a JavaScript VM (JSVM), including e.g. a WebAssembly JavaScript embedding in a web browser. Julia 1.2 This function requires at least Julia 1.2. source Base.Sys.loadavg – Function