C#•9mo ago

Object reference not set to an instance of an object

I'm making a simple UDP packet sender but for some reason I have this error when I attempt to start sending. which is "Object reference not set to an instance of an object. here is my code.

    public partial class Form1 : Form
    {
        private static string hexStream;
        private static UdpClient udpClient;
        private static byte[] packetData = { 0x01, 0x02 };

        public Form1()
        {
            InitializeComponent();
        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {
            string ipAddress = textBox1.Text;
        }

        private void checkBox2_CheckedChanged(object sender, EventArgs e)
        {
            if (checkBox2.Checked == true)
            {
                checkBox3.Checked = false;
                checkBox4.Checked = false;
                checkBox5.Checked = false;
            }

            if (checkBox6.Checked == true && checkBox2.Checked == true)
            {
                checkBox2.ForeColor = Color.Green;
            }
            else
            {
                checkBox2.ForeColor = Color.Black;
            }

            if (checkBox2.ForeColor == Color.Green)
            {
                int port = 80;
                UdpClient udpClient = new UdpClient();
                string ipAddress = textBox1.Text;

                Console.WriteLine();
                hexStream = Console.ReadLine();

                Console.WriteLine();
                int rate = int.Parse(Console.ReadLine());

                int interval = 1 / rate;

                udpClient.Send(packetData, packetData.Length, ipAddress, port);
            }
            else
            {
                udpClient.Close();
            }
        }

    public partial class Form1 : Form
    {
        private static string hexStream;
        private static UdpClient udpClient;
        private static byte[] packetData = { 0x01, 0x02 };

        public Form1()
        {
            InitializeComponent();
        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {
            string ipAddress = textBox1.Text;
        }

        private void checkBox2_CheckedChanged(object sender, EventArgs e)
        {
            if (checkBox2.Checked == true)
            {
                checkBox3.Checked = false;
                checkBox4.Checked = false;
                checkBox5.Checked = false;
            }

            if (checkBox6.Checked == true && checkBox2.Checked == true)
            {
                checkBox2.ForeColor = Color.Green;
            }
            else
            {
                checkBox2.ForeColor = Color.Black;
            }

            if (checkBox2.ForeColor == Color.Green)
            {
                int port = 80;
                UdpClient udpClient = new UdpClient();
                string ipAddress = textBox1.Text;

                Console.WriteLine();
                hexStream = Console.ReadLine();

                Console.WriteLine();
                int rate = int.Parse(Console.ReadLine());

                int interval = 1 / rate;

                udpClient.Send(packetData, packetData.Length, ipAddress, port);
            }
            else
            {
                udpClient.Close();
            }
        }

43 Replies

EthanOP•9mo ago

I am pretty sure it has to do with the "string ip Address = textBox1.Text" but I am relatively new and do not know how to fix it

Servator•9mo ago

private static UdpClient udpClient;

private static UdpClient udpClient;

You declared but didn't assign. use "new()" keyword.

Buddy•9mo ago

Next time, please show where the error occurs, you did not specify where the breakpoint hits / exception throws.

Servator•9mo ago

Also Why not radioBox ? It would fit your application. Don't bother with checkBox values Also check for constructor(s) for UdpClient

EthanOP•9mo ago

I dont know, I like checkboxes, do they raise any problems? k yeah its happening because of the chekcbox Where do I put that?

ACiDCA7•9mo ago

this code is quite messy string ipAddress = textBox1.Text; in textBox1_TextChanged doesnt do anything really UdpClient udpClient = new UdpClient(); in if (checkBox2.ForeColor == Color.Green) is only available in that if clause not on the else where you are trying to close the client and what default wrote

Servator•9mo ago

EthanOP•9mo ago

hmm, so how would I make it send when its green and not send when its not? Also I want to keep it secluded to like that checkbox if that makes sense

Servator•9mo ago

Check for constructors

EthanOP•9mo ago

like this?

EthanOP•9mo ago

Servator•9mo ago

Yeah you should see from there

EthanOP•9mo ago

ah how

Servator•9mo ago

One of them accepts IPEndPoint right ? So you can pass an ipEndPoint object

Servator•9mo ago

Like this

Buddy•9mo ago

I personally hate the wrappers, both Tcp / UDP wrappers are useless Raw sockets are way better

Servator•9mo ago

Yeah but it's easier to use/learn 😛

EthanOP•9mo ago

I have muy errors

EthanOP•9mo ago

Servator•9mo ago

Your C# version is older so you need to specify the type when using "new" keyword

EthanOP•9mo ago

sweet, that fixed it. however

EthanOP•9mo ago

Servator•9mo ago

Just read it man 😦 They are indicated with red underline

EthanOP•9mo ago

ok I read but do not understand

Servator•9mo ago

is a class not an object

Servator•9mo ago

It expects an object

Servator•9mo ago

this is an object That you created with "new" keyword.

EthanOP•9mo ago

that makes sense thank you

Servator•9mo ago

np 👍

EthanOP•9mo ago

sorry but 1 more thing

Servator•9mo ago

Just ask

EthanOP•9mo ago

Servator•9mo ago

It expects either just endPoint or hostname with port as you see But you are passing ipEndPoint object which is not a string

Servator•9mo ago

Hover the mouse on object and you can see it's type Which is "IPEndPoint?"

SinFluxx•9mo ago

They're presumably using the overload listed below that

Servator•9mo ago

Yeah I'm just explaining the fundamentals of IDE and logic behind objects You can pass ipEndPoint without port

        var ipEndPoint = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 80);

        using (var udpClient = new UdpClient(ipEndPoint))
        {
            var messageBytes = Encoding.UTF8.GetBytes("Hello World!");

            var bytesSent = udpClient.Send(messageBytes, messageBytes.Length, ipEndPoint);

            udpClient.Send(messageBytes, messageBytes.Length, ipEndPoint);

            Console.WriteLine($"Sent {bytesSent} bytes.");
        }

        var ipEndPoint = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 80);

        using (var udpClient = new UdpClient(ipEndPoint))
        {
            var messageBytes = Encoding.UTF8.GetBytes("Hello World!");

            var bytesSent = udpClient.Send(messageBytes, messageBytes.Length, ipEndPoint);

            udpClient.Send(messageBytes, messageBytes.Length, ipEndPoint);

            Console.WriteLine($"Sent {bytesSent} bytes.");
        }

EthanOP•9mo ago

oh ok yeah that makes some more sense now thank you for help

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Object reference not set to an instance of an object