Checking network status in C#

If you just want to check if the network is up then use:

bool networkUp
    = System.Net.NetworkInformation.NetworkInterface.GetIsNetworkAvailable();

To check a specific interface's status (or other info) use:

NetworkInterface[] networkCards
    = System.Net.NetworkInformation.NetworkInterface.GetAllNetworkInterfaces();

To check the status of a remote computer then you'll have to connect to that computer (see other answers)

If you want to monitor for changes in the status, use the System.Net.NetworkInformation.NetworkChange.NetworkAvailabilityChanged event:

NetworkChange.NetworkAvailabilityChanged 
    += new NetworkAvailabilityChangedEventHandler(NetworkChange_NetworkAvailabilityChanged);
_isNetworkOnline = NetworkInterface.GetIsNetworkAvailable();


// ...
void NetworkChange_NetworkAvailabilityChanged(object sender, NetworkAvailabilityEventArgs e)
{
    _isNetworkOnline  = e.IsAvailable;
}

First suggestion (IP connection)

You can try to connect to the IP address using something like:

IPEndPoint ipep = new IPEndPoint(Ipaddress.Parse("IP TO CHECK"), YOUR_PORT_INTEGER);
Socket server = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
server.Connect(ipep);

I suggest you to the check code of a "Chat" program. These programs manipulate a lot of IP connections and will give you a good idea of how to check if an IP is available.

Second suggestion (Ping)

You can try to ping. Here is a good tutorial. You will only need to do:

Ping netMon = new Ping();
PingResponse response = netMon.PingHost(hostname, 4);
if (response != null)
{
    ProcessResponse(response);
}