尝试在 WPF 中制作一个基本的 TCP 客户端
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Trying to make a basic TCP client in WPF
提问by Nick Falconer
I am trying to implement a basic TCP client in WPF. I have managed to to this using windows forms but can't get it working in WPF. I have tried going back to the very basics and adding things bit by bit. This is to connect to an arduino that is outputing single lines of code. I can successfully connect to it through telnet so the problem is with my code.
我正在尝试在 WPF 中实现一个基本的 TCP 客户端。我已经设法使用 Windows 窗体做到了这一点，但无法在 WPF 中使用它。我尝试回到最基本的东西，一点一点地添加东西。这是为了连接到输出单行代码的 arduino。我可以通过 telnet 成功连接到它，所以问题出在我的代码上。
This is what I have so far:
这是我到目前为止：
public partial class MainWindow : Window
{
private TcpClient tcp;
private StreamWriter SwSender;
private StreamReader SrReciever;
private Thread thrMessaging;
private delegate void UpdateLogCallBack(string strMessage);
public MainWindow()
{
InitializeComponent();
}
private void btn_Connect_Click(object sender, RoutedEventArgs e)
{
TcpClient tcp = new TcpClient();
txt_Log.AppendText("connecting");
tcp.Connect(IPAddress.Parse("192.168.137.1"), 2000);
txt_Log.AppendText("Connected");
thrMessaging = new Thread(new ThreadStart(ReceiveMessages));
thrMessaging.Start();
}
private void ReceiveMessages()
{
SrReciever = new StreamReader(tcp.GetStream());
while (true)
{
string response = SrReciever.ReadLine();
txt_Log.Dispatcher.Invoke(new UpdateLogCallBack(this.UpdateLog), new object[] { response });
}
}
private void UpdateLog(string strMessage)
{
txt_Log.AppendText(strMessage);
}
}
}
}
Running this gives me an error in the Receive messages method. It says the error is on the line with "SrReciever = new StreamReader(tcp.GetStream());" saying it a NullReferenceException, Object reference not set to an instance of an object.
运行此命令会导致我在 Receive messages 方法中出现错误。它说错误与“SrReciever = new StreamReader(tcp.GetStream());”有关 说它是 NullReferenceException，未将对象引用设置为对象的实例。
I'm not the best at programming, so if there is an example out there for a TCP client that works in WPF then that will be very helpful.
我不是最擅长编程，所以如果有一个在 WPF 中工作的 TCP 客户端的例子，那将非常有帮助。
Thanks Nick
谢谢尼克
回答by gideon
That is simply because you're creating a scoped variable here:
这仅仅是因为您在这里创建了一个作用域变量：
private void btn_Connect_Click(object sender, RoutedEventArgs e)
{
//TcpClient tcp = new TcpClient();
//this initialized a new tcp variable only here...
//do this instead...
tcp = new TcpClient();
//this will assign a new TcpClient to MainWindow.tcp
So what happens is MainWindow.tcpis actually null and then when ReceiveMessagesis called you are trying to call GetStream a null value.
所以发生的事情MainWindow.tcp实际上是空值，然后当ReceiveMessages被调用时，您试图将 GetStream 调用为空值。
