VB.NET【1】实现WebSocket【2】实时消息提醒系统
WebSocket是一种在单个TCP连接【3】上进行全双工通信【4】的协议，它允许服务器和客户端之间进行实时数据交换【5】。在VB.NET中，我们可以使用System.Net.WebSockets【6】命名空间来实现WebSocket通信。本文将介绍如何使用VB.NET创建一个WebSocket实时消息提醒系统，包括服务器端和客户端的实现。
系统需求
1. 服务器端：负责接收客户端的连接请求，接收和发送消息。
2. 客户端：负责连接到服务器，接收和显示消息。
服务器端实现
1. 创建项目
创建一个VB.NET控制台应用程序【7】。
2. 引入命名空间
在代码顶部引入必要的命名空间：
vb.net
Imports System.Net
Imports System.Net.WebSockets
Imports System.Text
Imports System.Threading
Imports System.Threading.Tasks
3. 创建WebSocket服务器类
创建一个名为`WebSocketServer【8】`的类，用于处理WebSocket连接和消息：
vb.net
Public Class WebSocketServer
Private ReadOnly _server As WebSocketServer
Private ReadOnly _sockets As New List(Of WebSocket)
Public Sub New(ByVal localIp As String, ByVal localPort As Integer)
_server = New WebSocketServer(localIp, localPort)
AddHandler _server.Opened, AddressOf OnClientConnected
AddHandler _server.CloseRequest, AddressOf OnClientDisconnected
AddHandler _server.Error, AddressOf OnClientError
End Sub
Public Sub Start()
_server.Start()
End Sub
Public Sub StopServer()
_server.Stop()
End Sub
Private Sub OnClientConnected(ByVal sender As Object, ByVal e As WebSocketServerEventArgs)
Dim socket As WebSocket = e.WebSocket
_sockets.Add(socket)
Console.WriteLine("Client connected: " & socket.RemoteEndPoint.ToString())
End Sub
Private Sub OnClientDisconnected(ByVal sender As Object, ByVal e As WebSocketServerEventArgs)
Dim socket As WebSocket = e.WebSocket
_sockets.Remove(socket)
Console.WriteLine("Client disconnected: " & socket.RemoteEndPoint.ToString())
End Sub
Private Sub OnClientError(ByVal sender As Object, ByVal e As WebSocketServerEventArgs)
Console.WriteLine("Client error: " & e.Exception.Message)
End Sub
Public Sub SendToAll(ByVal message As String)
For Each socket As WebSocket In _sockets
If socket.State = WebSocketState.Open Then
Dim encodedMessage As Byte() = Encoding.UTF8.GetBytes(message)
socket.SendAsync(New ArraySegment(Of Byte)(encodedMessage), WebSocketMessageType.Text, True, CancellationToken.None)
End If
Next
End Sub
End Class
4. 启动服务器
在`Main`方法中启动服务器：
vb.net
Public Shared Sub Main()
Dim server As New WebSocketServer("127.0.0.1", 8080)
server.Start()
Console.WriteLine("WebSocket server started. Press Enter to exit.")
Console.ReadLine()
server.StopServer()
End Sub
客户端实现
1. 创建项目
创建一个VB.NET控制台应用程序。
2. 引入命名空间
在代码顶部引入必要的命名空间：
vb.net
Imports System.Net.WebSockets
Imports System.Text
Imports System.Threading.Tasks
3. 创建WebSocket客户端类
创建一个名为`WebSocketClient【9】`的类，用于连接服务器和接收消息：
vb.net
Public Class WebSocketClient
Private ReadOnly _client As ClientWebSocket
Public Sub New(ByVal uri As Uri)
_client = New ClientWebSocket()
AddHandler _client.Opened, AddressOf OnClientOpened
AddHandler _client.MessageReceived, AddressOf OnClientMessageReceived
AddHandler _client.Error, AddressOf OnClientError
End Sub
Public Sub Connect()
_client.ConnectAsync(uri, CancellationToken.None).Wait()
End Sub
Public Sub Send(ByVal message As String)
Dim encodedMessage As Byte() = Encoding.UTF8.GetBytes(message)
_client.SendAsync(New ArraySegment(Of Byte)(encodedMessage), WebSocketMessageType.Text, True, CancellationToken.None)
End Sub
Public Sub Close()
_client.CloseAsync(WebSocketCloseStatus.NormalClosure, String.Empty, CancellationToken.None)
End Sub
Private Sub OnClientOpened(ByVal sender As Object, ByVal e As WebSocketOpenEventArgs)
Console.WriteLine("Connected to server.")
End Sub
Private Sub OnClientMessageReceived(ByVal sender As Object, ByVal e As WebSocketMessageReceivedEventArgs)
Dim message As String = Encoding.UTF8.GetString(e.Message.Array, e.Message.Offset, e.Message.Count)
Console.WriteLine("Received message: " & message)
End Sub
Private Sub OnClientError(ByVal sender As Object, ByVal e As WebSocketErrorEventArgs)
Console.WriteLine("Client error: " & e.Exception.Message)
End Sub
End Class
4. 连接到服务器并接收消息
在`Main`方法中连接到服务器并接收消息：
vb.net
Public Shared Sub Main()
Dim client As New WebSocketClient(New Uri("ws://127.0.0.1:8080"))
client.Connect()
Console.WriteLine("Press Enter to send a message.")
Console.ReadLine()
client.Send("Hello, server!")
Console.WriteLine("Press Enter to close the connection.")
Console.ReadLine()
client.Close()
End Sub
总结
本文介绍了如何使用VB.NET实现WebSocket实时消息提醒系统。通过创建服务器端和客户端，我们能够实现客户端与服务器之间的实时通信。在实际应用中，可以根据需求扩展功能，如添加用户认证【10】、消息加密【11】等。
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