How do I keep a socket open and keep writing to it?

So the solution came down to declaring the socket oustide the main class "IMessageBasedSession session;" and then making a new instance in side the main class. That way the socket is left open and the other classes could access the socket without making a new instance. I also had to do the same in the form for accesing the class and keeping the same IP going. Below are snippets:

using Ivi.Visa;
using Ivi.Visa.FormattedIO;
using System;
using System.Windows.Forms;
using System.IO;

namespace Refresh
{
    internal class SessionClass
    {

        IMessageBasedSession session;
        MessageBasedFormattedIO formattedIO;

        public SessionClass(string strIP)
        {
            try
            {
                //Start the socket 
                string VISA_ADDRESS = "TCPIP::" + strIP + "::5025::SOCKET";
                session = GlobalResourceManager.Open(VISA_ADDRESS) as IMessageBasedSession;
                session.TerminationCharacterEnabled = true;

                formattedIO = new MessageBasedFormattedIO(session);
            }
            catch (Exception ex)
            {
                MessageBox.Show("Unable to start connection to " + strIP + ". Make sure the equipment is on and the address is correct. \n Error code follows:\n" + ex, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }

        }

        public bool SendSCPIandGetResponse(string strSendMe, out string strOut)
        {
            strOut = "";
            try
            {
                formattedIO.WriteLine(strSendMe);
                strOut = formattedIO.ReadLine();
                return false;
            }
            catch (Exception err)
            {
                if (err.HResult == -2146233088)
                {
                    MessageBox.Show("Check to see if the Spectrum Analyzer is ON and the IP address for the Spectrum Analyzer is correct. Fault from SendSCPIandGetResponse", "Device not found", MessageBoxButtons.OK, MessageBoxIcon.Error);
                    return true;
                }
                else
                {
                    MessageBox.Show(err.Message.ToString());
                    return true;
                }
            }
        }

        public bool SendSCPI(string strSendMe)
        {
            try
            {
                formattedIO.WriteLine(strSendMe);
                return false;
            }
            catch (Exception err)
            {
                if (err.HResult == -2146233088)
                {
                    MessageBox.Show("Check to see if the Spectrum Analyzer is ON and the IP address for the Spectrum Analyzer is correct. Fault from SendSCPI", "Device not found", MessageBoxButtons.OK, MessageBoxIcon.Error);
                    // Closes the program.
                    return true;
                }
                else
                {
                    MessageBox.Show(err.Message.ToString());
                    // Closes the program.
                    return true;
                }
            }
        }

        public void Close()
        {
            session.Dispose();
        }
 }

using System;
using System.ComponentModel;
using System.Linq;
using System.Windows.Forms;
using System.Xml;

namespace Refresh
{
    public partial class SpecAnControls : Form
    {
        TestClass testClass = new TestClass();
        //start SessionClass reference at form level and create new instance later to pass variable
        SessionClass SessionClass;
        //Create a new instance of XML document to use through the form
        XmlDocument doc = new XmlDocument();

        //SpecAnControls is the "main form" for this form.
        public SpecAnControls(string strSA_internal_name, string strIP_use)
        {
            //see if SpecAn communicates and if it does not disable the controls.
            bool blnContinue = Poll_SA_Class();
            if (blnContinue == true)
            {
                SessionClass = new SessionClass(strIP_use);

            }

        }
    }
}

So my thing did not work, please help.

Thank you both for your help, I think the biggest problem is I do not know how to ask this properly. I will try to clarify and please forgive me. Also when typing this up, I think I got close

Curently I have the main form using one IP and then 4 buttons that call the same child form and passes the IP address to each form upon button click. Each form will control the IP address, so I lead you on the wrong direction (sorry again). 

What I want to do is have class like calls that I can use with the form controls like:

using System;
using System.Windows.Forms;
namespace MyApplication
{

  public partial class Form1 : Form
  {
    mySessions mySession = new mySessions;
        public Main(string strIP)
        {
            InitializeComponent();    
        mySession.start(strIP);
      }

        private void button1_Click(object sender, EventArgs e)
      {
        mySession.write(strMessage);
      }

        private void button2_Click(object sender, EventArgs e)
      {
        mySession.read(strMessage, strResponse);
      }

      private void closeButtonPressed(string[] args)
      {
        mySession.close();
  }

and structure the class like:

using System;
using System.Collections.Generic;
using System.Text;
using Ivi.Visa;
using Ivi.Visa.FormattedIO;

namespace MyApplication
{
   class mySessions
    {
        static void start(string strIP)
        {
            // Change this variable to the address of your instrument
            string VISA_ADDRESS = "TCPIP::" + strIP + ":::5025::SOCKET";

            // Create a connection (session) to the TCP/IP socket on the instrument. 

            IMessageBasedSession session = GlobalResourceManager.Open(VISA_ADDRESS) as IMessageBasedSession;
            session.TerminationCharacterEnabled = true;
        }

        static void write(string strMessage)
      {
            // Send the cmd
            MessageBasedFormattedIO formattedIO = new MessageBasedFormattedIO(session);
            formattedIO.WriteLine(strMessage);
      }
        static void read(string strMessage, string strResponse)
        { 
          // Send the cmd and read the response as strings
            MessageBasedFormattedIO formattedIO = new MessageBasedFormattedIO(session);
            formattedIO.WriteLine(strMessage);
            string strResponse= formattedIO.ReadLine();
      }

        static void close()
      {
            // Close the connection to the instrument
            session.Dispose();
      }

   }
}
 

using System;
using System.Collections.Generic;
using System.Text;
using Ivi.Visa;
using Ivi.Visa.FormattedIO;

namespace Socket_Example
{
  class Program
  {
    static void Main(string[] args)
    {
      // List to store open sessions for 5 IP addresses
      List sessions = new List();

      // Define your 5 instrument IP addresses
      string[] instrumentAddresses = new string[] {
        "TCPIP::169.254.104.51::5025::SOCKET",
        "TCPIP::169.254.104.52::5025::SOCKET",
        // ... add remaining 3 IP addresses
      };

      // Open sessions for each IP address
      foreach (string address in instrumentAddresses)
      {
        IMessageBasedSession session = GlobalResourceManager.Open(address) as IMessageBasedSession;
        session.TerminationCharacterEnabled = true;
        sessions.Add(session);
      }

      // Example: Write commands to each open socket
      foreach (IMessageBasedSession session in sessions)
      {
        MessageBasedFormattedIO formattedIO = new MessageBasedFormattedIO(session);
        formattedIO.WriteLine("*IDN?"); // Example command
        string response = formattedIO.ReadLine();
        Console.WriteLine("Response from {0}: {1}", session.ResourceName, response);
      }

      // Close all sessions at the end (optional for persistent connections)
      foreach (IMessageBasedSession session in sessions)
      {
        session.Dispose();
      }

      Console.WriteLine("Press any key to exit...");
      Console.ReadKey();
    }
  }
}

• Modify the instrumentAddresses array to include your actual IP addresses.
• Replace the example *IDN? command with your desired instrument commands within the loop.

This example opens and closes the socket connection for each instrument communication. This isn't ideal for your scenario where you want to keep the connection open for multiple commands.

To keep a socket open and continuously write to it without closing it after each write, you can keep the socket open within a loop.

using System;
using Ivi.Visa;
using Ivi.Visa.FormattedIO;

namespace Socket_Example
{
    class Program
    {
        static void Main(string[] args)
        {
            // Change this variable to the address of your instrument
            string VISA_ADDRESS = "Your instrument's VISA address goes here!";

            // Create a connection (session) to the TCP/IP socket on the instrument. 
            // Change VISA_ADDRESS to a SOCKET address, e.g. "TCPIP::169.254.104.59::5025::SOCKET"
            using (IMessageBasedSession session = GlobalResourceManager.Open(VISA_ADDRESS) as IMessageBasedSession)
            {
                // The first thing you should do with a SOCKET connection is enable the Termination Character. Otherwise all of your read's will fail
                session.TerminationCharacterEnabled = true;

                // We can find out details of the connection
                ITcpipSocketSession socket = session as ITcpipSocketSession;
                Console.WriteLine($"IP: {socket.Address}\r\nHostname: {socket.HostName}\r\nPort: {socket.Port}\r\n");

                // Create a formatted I/O object for writing to the socket
                MessageBasedFormattedIO formattedIO = new MessageBasedFormattedIO(session);

                // You can now write to the socket within a loop or as needed
                while (true) // This loop will continue indefinitely until you manually stop it
                {
                    // Send your commands to the instrument
                    formattedIO.WriteLine("*IDN?");
                    string idnResponse = formattedIO.ReadLine();
                    Console.WriteLine("*IDN? returned: {0}", idnResponse);

                    // Add a delay if necessary before sending the next command
                    System.Threading.Thread.Sleep(1000);
                }
            }

            // The connection will be automatically closed when it goes out of scope due to "using" block
        }
    }
}