try块未捕获TcpClient连接异常

Question

我正在VB.Net中打开一个TcpClient连接，并将那部分代码放在try / catch块中。 但是当IP地址不可用时，编译后的程序仍然因未处理的异常而崩溃。

Try
    ' Open connection 
    Dim client As System.Net.Sockets.TcpClient = New System.Net.Sockets.TcpClient
    client.Connect(Printer.IpAddress, Printer.Port)
    ' Write ZPL String to connection 
    Dim writer As System.IO.StreamWriter = New System.IO.StreamWriter(client.GetStream(), System.Text.Encoding.GetEncoding(1252))
    writer.Write(EtikettText)
    writer.Flush()
    ' Close Connection 
    writer.Close()
    client.Close()
Catch ex As Exception
    MsgBox(ex.Message, MsgBoxStyle.OkOnly Or MsgBoxStyle.Critical, "Druckerfehler")
    lastex = ex
    Return False
End Try

我认为这种常规的try / catch可以捕获所有异常。 但是程序在此调用堆栈中崩溃：

错误：无法建立连接，因为目标计算机拒绝了连接192.168.1.158:9100

堆栈跟踪：

at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress)
at System.Net.Sockets.Socket.Connect(EndPoint remoteEP)
at System.Net.Sockets.TcpClient.Connect(IPEndPoint remoteEP)
at System.Net.Sockets.TcpClient.Connect(IPAddress address, Int32 port)
at Cocos.ChargenEtikett.Print()