You shouldn't just use one IP address, as there may be more than one ipv4 addresses.
List<IPAddress> localAddresses = new List<IPAddress>();
foreach (IPAddress ipAddress in Dns.GetHostEntry(Dns.GetHostName()).AddressList)
{
if (ipAddress.AddressFamily == AddressFamily.InterNetwork)
{
localAddresses.Add(ipAddress);
}
}