Check if a server is available

Question

I'm looking for a way to check if a server is still available. We have a offline application that saves data on the server, but if the serverconnection drops (it happens occasionally), we have to save the data to a local database instead of the online database. So we need a continues check to see if the server is still available.

We are using C# for this application

The check on the sqlconnection.open is not really an option because this takes about 20 sec before an error is thrown, we can't wait this long + I'm using some http services as well.

Answer 1

Just use the System.Net.NetworkInformation.Ping class. If your server does not respond to ping (for some reason you decided to block ICMP Echo request) you'll have to invent your own service for this. Personally, I'm all for not blocking ICMP Echo requests, and I think this is the way to go. The ping command has been used for ages to check reachability of hosts.

using System.Net.NetworkInformation;
var ping = new Ping();
var reply = ping.Send("google.com", 60 * 1000); // 1 minute time out (in ms)
// or...
reply = ping.Send(new IPAddress(new byte[]{127,0,0,1}), 3000);

Answer 2

From your question it appears the purpose of connecting to the server is to use its database. Your priority must be to check whether you can successfully connect to the database. It doesn't matter if you can PING the server or get an HTTP response (as suggested in other answers), your process will fail unless you successfully establish a connection to the database. You mention that checking a database connection takes too long, why don't you just change the Connection Timeout setting in your application's connection string to a more impatient value such as 5 seconds (Connection Timeout=5)?