Question

我有客户端服务器应用程序（Lan base）。最初，客户端应用程序成功连接到服务器，但稍后在运行时由于某种原因（例如服务器计算机关闭）导致连接丢失。这会触发类似UNABLE TO CONNECT TO HOST的错误。如何在运行时检查连接状态？

代码如下

连接类

using MySql.Data.MySqlClient;  
namespace Connection_Checker
{
 public class Connection
 {
   public static MySqlConnection cnn = new MySqlConnection("Server=localhost;Database=arc;User Id=root;Password=root;");
 }
}

表格

private void Form1_Load(object sender, EventArgs e)
{
  Connection.cnn.Open();
}

//and timer
private void timer1_Tick(object sender, EventArgs e)
{
  if (Connection.cnn.State == ConnectionState.Open)
  {
    this.Text = "Connected";
  }
  else
  {
    this.Text = "Disconnected";
    return; 
  }
}

我的计时器是enable = true

Answer 1

如果我是你的形式，我不会在表单加载事件中打开连接。

相反，我将获取数据的方法将是这样的

using MySql.Data.MySqlClient;  
namespace Connection_Checker
{
 public class Connection
 {
     public static connectionString = "Server=localhost;Database=arc;User Id=root;Password=root;";
 }
}

以表格

private void GetData()
{
 try{
     using (MySqlSqlConnection connection = new MySqlSqlConnection(Connection.connectionString ))
     {
       connection.Open();
       //GetData
        connection.Close();
      }
 }
 catch
 {
     MessageBox.Show("An error occurred while trying to fetch Data");
 }
}

private void Form1_Load(object sender, EventArgs e)
{
  //I would avoid this. 
  // Connection.cnn.Open();
}

//I am not sure why you are having this.
private void timer1_Tick(object sender, EventArgs e)
{
  //if (Connection.cnn.State == ConnectionState.Open)
  //{
  //  this.Text = "Connected";
  //}
  //else
  //{
  //  this.Text = "Disconnected";
  //  return; 
  //}
}

Answer 2

捕获传输错误不会告诉您何时连接失败。它只告诉您在尝试使用它时连接不可用。

根据您的示例使用计时器进行连续状态监控，使用此扩展方法直接查询TCP连接状态。

public static class Extensions
{
  /// <summary>
  /// Obtain the current state of the socket underpinning a TcpClient.
  /// Unlike TcpClient.Connected this is reliable and does not require 
  /// capture of an exception resulting from a failed socket write.
  /// </summary>
  /// <param name="tcpClient">TcpClient instance</param>
  /// <returns>Current state of the TcpClient.Client socket</returns>
  public static TcpState GetState(this TcpClient tcpClient)
  {
    var foo = IPGlobalProperties.GetIPGlobalProperties().GetActiveTcpConnections()
      .SingleOrDefault(x => x.LocalEndPoint.Equals(tcpClient.Client.LocalEndPoint));
    return foo != null ? foo.State : TcpState.Unknown;
  }
}

但是，正如其他人在评论中已经提到的那样，您对连续连接的依赖可能反映了您的应用程序中的严重设计缺陷。你应该留意你给出的建议并重新设计你的应用程序。占用连接会严重限制可扩展性，并且不会让您受到网络管理员或数据库管理员的欢迎。

如何使用C＃.net（winforms）在运行时检查连接状态

2 个答案: