Implement a basic IP Scanner for a local LAN in C#

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Introduction

This is a very basic IP Scanner written in C#. I searched a long time and couldn't find something done in C# similar to what I wrote. So I decided to put it on the Code Project.

Ok.. now how to implement it ?

For those of you who have written a TCP/IP program it's more than easy... Basically after getting the From .. To IPAddresses, all you do is, call  Dns.GetHostByAddress.

Here is the most important part of the App:

try
{
    
  string address = ipTo.Text.Substring(0,lastT+1);
  System.Diagnostics.Debug.WriteLine(ipTo.Text.Substring(0,lastT+1)+i);
  IPHostEntry he = Dns.GetHostByAddress( address+i);
  Add( he.HostName );
  result += 1;
}
catch( SocketException )
{
  // in cazul unei erori : Romanian for -> in case of an error
}
catch( Exception )
{
  // previne bloacarea programului
 
}// it prevents the App from crashing

Ok , that's it ... yes .. for the implementation, get the code Or copy/paste this >...

/*
* Author : Lazar Mihai
* 
* It shows how to do simple scan of the network inside a local LAN.
* 
* The program is straith forward for any questions, comments or sugestions
* please write me an e -mail at : sharpoverride@gmail.com 
* 
* */
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Net;
using System.Net.Sockets;
using System.Threading;

namespace GetStations
{
  /// <summary>
  /// Summary description for Form1.
  /// </summary>
  public class Form1 : System.Windows.Forms.Form
  { 
    private System.Windows.Forms.Label label1;

    private System.Windows.Forms.Label label2;
    private System.Windows.Forms.TextBox ipFrom;
    private System.Windows.Forms.TextBox ipTo;
    private System.Windows.Forms.TextBox hostName;
    private System.Windows.Forms.Button btnUse;
    private System.Windows.Forms.ListBox add;
    private System.Windows.Forms.Label label3;
    private System.Windows.Forms.Button btnStart;
    /// <summary>
    /// Required designer variable.
    /// </summary>
    private System.ComponentModel.Container components = null;

    public Form1()
    {
      //
      // Required for Windows Form Designer support
      //
      InitializeComponent();

      //
      // TODO: Add any constructor code after InitializeComponent call
      //
      LoadMe();
    }
    void LoadMe()
    {
      hostName.Text = Dns.GetHostName();
    }

    /// <summary>
    /// Clean up any resources being used.
    /// </summary>
    protected override void Dispose( bool disposing )
    {
      if( disposing )
      {
        if (components != null) 
        {
          components.Dispose();
        }
      }
      base.Dispose( disposing );
    }

    #region Windows Form Designer generated code
    /// <summary>
    /// Required method for Designer support - do not modify
    /// the contents of this method with the code editor.
    /// </summary>
    private void InitializeComponent()
    {
      this.label1 = new System.Windows.Forms.Label();
      this.label2 = new System.Windows.Forms.Label();
      this.ipFrom = new System.Windows.Forms.TextBox();
      this.ipTo = new System.Windows.Forms.TextBox();
      this.hostName = new System.Windows.Forms.TextBox();
      this.btnUse = new System.Windows.Forms.Button();
      this.add = new System.Windows.Forms.ListBox();
      this.label3 = new System.Windows.Forms.Label();
      this.btnStart = new System.Windows.Forms.Button();
      this.SuspendLayout();
      // 
      // label1
      // 
      this.label1.Location = new System.Drawing.Point(32, 32);
      this.label1.Name = "label1";
      this.label1.Size = new System.Drawing.Size(88, 24);
      this.label1.TabIndex = 0;
      this.label1.Text = "Ip Range:";
      this.label1.TextAlign = System.Drawing.ContentAlignment.MiddleCenter;
      // 
      // label2
      // 
      this.label2.Location = new System.Drawing.Point(32, 64);
      this.label2.Name = "label2";
      this.label2.Size = new System.Drawing.Size(88, 24);
      this.label2.TabIndex = 1;
      this.label2.Text = "Host :";
      this.label2.TextAlign = System.Drawing.ContentAlignment.MiddleCenter;
      // 
      // ipFrom
      // 
      this.ipFrom.Location = new System.Drawing.Point(128, 32);
      this.ipFrom.Name = "ipFrom";
      this.ipFrom.Size = new System.Drawing.Size(160, 20);
      this.ipFrom.TabIndex = 2;
      this.ipFrom.Text = "127.0.0.1";
      // 
      // ipTo
      // 
      this.ipTo.Location = new System.Drawing.Point(328, 32);
      this.ipTo.Name = "ipTo";
      this.ipTo.Size = new System.Drawing.Size(160, 20);
      this.ipTo.TabIndex = 3;
      this.ipTo.Text = "127.0.0.1";
      // 
      // hostName
      // 
      this.hostName.Location = new System.Drawing.Point(128, 64);
      this.hostName.Name = "hostName";
      this.hostName.Size = new System.Drawing.Size(128, 20);
      this.hostName.TabIndex = 4;
      this.hostName.Text = "";
      // 
      // btnUse
      // 
      this.btnUse.Location = new System.Drawing.Point(280, 64);
      this.btnUse.Name = "btnUse";
      this.btnUse.Size = new System.Drawing.Size(40, 24);
      this.btnUse.TabIndex = 5;
      this.btnUse.Text = "Use";
      this.btnUse.Click += new System.EventHandler(this.UseClick);
      // 
      // add
      // 
      this.add.Location = new System.Drawing.Point(64, 120);
      this.add.Name = "add";
      this.add.Size = new System.Drawing.Size(552, 264);
      this.add.TabIndex = 6;
      // 
      // label3
      // 
      this.label3.Location = new System.Drawing.Point(296, 32);
      this.label3.Name = "label3";
      this.label3.Size = new System.Drawing.Size(24, 24);
      this.label3.TabIndex = 7;
      this.label3.Text = "to";
      this.label3.TextAlign = System.Drawing.ContentAlignment.MiddleCenter;
      // 
      // btnStart
      // 
      this.btnStart.Location = new System.Drawing.Point(432, 64);
      this.btnStart.Name = "btnStart";
      this.btnStart.Size = new System.Drawing.Size(112, 40);
      this.btnStart.TabIndex = 8;
      this.btnStart.Text = "Start !";
      this.btnStart.Click += new System.EventHandler(this.StartClick);
      // 
      // Form1
      // 
      this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
      this.ClientSize = new System.Drawing.Size(680, 422);
      this.Controls.Add(this.btnStart);
      this.Controls.Add(this.label3);
      this.Controls.Add(this.add);
      this.Controls.Add(this.btnUse);
      this.Controls.Add(this.hostName);
      this.Controls.Add(this.ipTo);
      this.Controls.Add(this.ipFrom);
      this.Controls.Add(this.label2);
      this.Controls.Add(this.label1);
      this.Name = "Form1";
      this.Text = "Find network";
      this.ResumeLayout(false);

    }
    #endregion

    void Add( string m )
    {
      add.Items.Add( m );
    }
    /// <summary>
    /// The main entry point for the application.
    /// </summary>
    [STAThread]
    static void Main() 
    {
      Application.Run(new Form1());
    }

    private void UseClick(object sender, System.EventArgs e)
    {
      //When pressing the use use button
    
      IPHostEntry ip = Dns.GetHostByName( Dns.GetHostName() );
      ipFrom.Text = ip.AddressList[0].ToString();
      ipTo.Text = ip.AddressList[0].ToString();


    }
    Thread sercher ;
 
    private void StartClick(object sender, System.EventArgs e)
    {
      sercher = new Thread( new ThreadStart( Find ));
      add.Items.Clear();
      try
      {
        IPAddress from = IPAddress.Parse( ipFrom.Text );
        IPAddress to = IPAddress.Parse( ipTo.Text );
      }
      catch( FormatException fe )
      {
        MessageBox.Show( fe.Message );
        return;
      }
      sercher.Name = "Network searching thread";
      sercher.Start();
      add.Items.Add( "-->> >>> Please wait while processing is done <<< <<--" );
      Thread.Sleep(1);// pune la culcare Threadul principal

    }
    /// <summary>
    /// 
    /// </summary>
    void Find( ) // 
    {
      Add( "-- >>> >> >>> Found station <<< << <<< -- " );
      int lastF = ipFrom.Text.LastIndexOf(".");
      int lastT = ipTo.Text.LastIndexOf(".");
      string frm = ipFrom.Text.Substring(lastF+1);
      string tto = ipTo.Text.Substring(lastT+1);
      int result = 0;
      System.Diagnostics.Debug.WriteLine( frm + " " + tto);
      for( int i = int.Parse( frm); i <= int.Parse(tto );i++)
      {
        try
        {
          string address = ipTo.Text.Substring(0,lastT+1);
          System.Diagnostics.Debug.WriteLine(ipTo.Text.Substring(0,lastT+1)+i);
          IPHostEntry he = Dns.GetHostByAddress( address+i);
          Add( he.HostName );
          result += 1;
        }

        catch( SocketException )
        {
          // in cazul unei erori
        }
        catch( Exception )
        {
          // previne bloacarea programului
        }
      }

    }
  }

}