用VB.net编写客户端，含心跳机制和掉线重连

在 VB.NET 中编写一个含有心跳机制和掉线重连的客户端可以通过以下步骤实现：

1. 导入必要的命名空间：

Imports System
Imports System.Net
Imports System.Net.Sockets
Imports System.Threading

2. 创建一个类来管理客户端连接和通信：

Public Class Client
    Private clientSocket As TcpClient
    Private serverIP As String
    Private serverPort As Integer
    Private isConnected As Boolean
    Private heartbeatTimer As Timer

    Public Sub New(ByVal ip As String, ByVal port As Integer)
        serverIP = ip
        serverPort = port
        isConnected = False
        heartbeatTimer = New Timer(AddressOf SendHeartbeat, Nothing, Timeout.Infinite, Timeout.Infinite)
    End Sub

    Public Sub Connect()
        Try
            clientSocket = New TcpClient()
            clientSocket.Connect(serverIP, serverPort)
            isConnected = True
            StartHeartbeat()
            StartListening()
        Catch ex As Exception
            Console.WriteLine("Failed to connect to the server: " & ex.Message)
        End Try
    End Sub

    Public Sub Disconnect()
        isConnected = False
        clientSocket.Close()
        StopHeartbeat()
    End Sub

    Private Sub StartHeartbeat()
        heartbeatTimer.Change(0, Timeout.Infinite)
    End Sub

    Private Sub StopHeartbeat()
        heartbeatTimer.Change(Timeout.Infinite, Timeout.Infinite)
    End Sub

    Private Sub SendHeartbeat(ByVal state As Object)
        ' 发送心跳消息给服务器
        Dim heartbeatMessage As String = "Heartbeat"
        Dim data As Byte() = System.Text.Encoding.ASCII.GetBytes(heartbeatMessage)
        Dim stream As NetworkStream = clientSocket.GetStream()
        stream.Write(data, 0, data.Length)
        Console.WriteLine("Sent heartbeat to server")

        ' 设置下一次心跳发送的时间间隔
        heartbeatTimer.Change(5000, Timeout.Infinite)
    End Sub

    Private Sub StartListening()
        Dim receiveThread As New Thread(AddressOf ReceiveData)
        receiveThread.Start()
    End Sub

    Private Sub ReceiveData()
        While isConnected
            Try
                Dim stream As NetworkStream = clientSocket.GetStream()
                Dim buffer(clientSocket.ReceiveBufferSize) As Byte
                Dim bytesRead As Integer = stream.Read(buffer, 0, clientSocket.ReceiveBufferSize)
                Dim receivedData As String = System.Text.Encoding.ASCII.GetString(buffer, 0, bytesRead)
                Console.WriteLine("Received data from server: " & receivedData)

                ' 处理接收到的数据
                ' ...

            Catch ex As Exception
                Console.WriteLine("Lost connection to the server: " & ex.Message)
                Reconnect()
            End Try
        End While
    End Sub

    Private Sub Reconnect()
        ' 重新连接服务器
        While Not isConnected
            Try
                clientSocket = New TcpClient()
                clientSocket.Connect(serverIP, serverPort)
                isConnected = True
                StartHeartbeat()
                StartListening()
                Console.WriteLine("Reconnected to the server")
            Catch ex As Exception
                Console.WriteLine("Failed to reconnect to the server: " & ex.Message)
                Thread.Sleep(5000) ' 等待 5 秒后重试
            End Try
        End While
    End Sub
End Class

3. 在主程序中使用客户端类：

Public Class MainProgram
    Public Shared Sub Main()
        Dim serverIP As String = "127.0.0.1" ' 服务器的 IP 地址
        Dim serverPort As Integer = 1234 ' 服务器的端口号

        Dim client As New Client(serverIP, serverPort)
        client.Connect()

        ' 执行其他操作
        ' ...

        client.Disconnect()
    End Sub
End Class

以上代码会创建一个名为 `Client` 的客户端类，其中包含了连接服务器、发送心跳消息、接收数据、处理断线重连等功能。你可以根据实际需求修改代码，比如添加数据处理的逻辑、更好的错误处理等。