Ho to get i Device Port No. and Name

add reference system.management from the com tab.

using System.Management

ManagementObjectSearcher mos = new ManagementObjectSearcher("SELECT * FROM Win32_POTSModem");

            foreach (ManagementObject mo in mos.Get())

            {

                // for modem name

                listBox1.Items.Add(mo["Caption"].ToString());

  // for modem port

                listBox1.Items.Add(mo["AttachedTo"].ToString());

            }

For more setting you can visit this link.

http://msdn.microsoft.com/en-us/library/aa394360(VS.85).aspx

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