Server Alive

I have written an application that runs stand alone on a users machine without being on the company's network. However, there are certain pieces that requires the user to be on the network. I would like to disable these if the user is not on the network. Currently I have a method that checks if a directory path exists (a network directory) to determine if the user is on the network. This has proved inefficient as it sometimes takes a few seconds for the method to work. I need something more efficient to let me know if the user is on the company's network

SystemInformation.Network just tells me if a network is present regardless if it is the company's network or some other the user has connected themselves to. Thus this property would not help me

Any insights would be great!

Andrew
Thu May 13 14:39:11 CDT 2004

I'd suggest you look into using a 'ping', its lightweight and fast. There
are a number of examples showing how to do this in .Net.

Check the link below for one example:
http://www.gotdotnet.com/Community/UserSamples/Details.aspx?SampleGuid=eb1cfcb2-9b1f-4265-8a81-d43fef46552a

Good luck.

-Andrew

anonymous
Thu May 13 16:46:03 CDT 2004

Andrew

I tried the example you cited - it ALWAYS returns false even when in fact I am connected. I use the dos ping utility and it returns replies but when I use the code in that example it returns false. Here is the code, perhaps you or someone else could tell whats wrong

public class Pin

IPAddress hostadd
int timeout_ms
string last_error = ""
string resolved_ip_address = ""

// this is the default constructo
public Ping(

/
// TODO: Add constructor logic her
/
timeout_ms = 10000000; // 2s


// this constructor allows the timeout value to be specified
public Ping(int a_timeout_ms

/
// TODO: Add constructor logic her
/
timeout_ms = a_timeout_ms * 1000; // tmo in millisecond


// returns the last network erro
public string LastErro

ge

return last_error



public string IpAddres

ge

return resolved_ip_address



public bool CheckByNameOrIP(String vw_name


tr

// try to resolve the name using DN
hostadd = Dns.Resolve(vw_name).AddressList[0]

catch (System.Net.Sockets.SocketException ex

last_error = ex.Message
return false


return local_ping()



public bool CheckByIpAddr(String ip_addr

tr

hostadd = IPAddress.Parse(ip_addr)

catch (System.Net.Sockets.SocketException ex

last_error = ex.Message
return false


return local_ping()


private bool local_ping(

const int SEND_SIZE = 16
const int RECEIVE_SIZE = 200
const int ECHO_PORT = 7

resolved_ip_address = hostadd.ToString()

//Set up variables and String to write to the serve
byte[] SendBytes = new byte[SEND_SIZE]
byte[] RecvBytes = new byte[RECEIVE_SIZE]

// IPAddress and IPEndPoint represent the endpoint that wil
// receive the reques
// Get first IPAddress in list return by DN

int rcvd
IPEndPoint EPhost
int sent

tr

// Echo is served by port
EPhost = new IPEndPoint(hostadd, ECHO_PORT)

//Create the Socket for sending ICMP data
Socket s = new Socket(AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.Icmp)

// Send the PING to the hos
SendBytes[0] = 8
SendBytes[1] = 0
SendBytes[2] = 0xF7
SendBytes[3] = 0xFF
SendBytes[4] = 0
SendBytes[5] = 0
SendBytes[6] = 0
SendBytes[7] = 0
SendBytes[8] = 0
SendBytes[9] = 0
SendBytes[10] = 0
SendBytes[11] = 0
SendBytes[12] = 0
SendBytes[13] = 0
SendBytes[14] = 0
SendBytes[15] = 0

// send the ECH
sent = s.SendTo(SendBytes, SEND_SIZE, SocketFlags.None, EPhost)

ArrayList cr = new ArrayList()
cr.Add(s)

//now receive the ECHO respons
Socket.Select(cr, null, null, timeout_ms); //1 sec select time in microsecond

if (cr.Count > 0

rcvd = s.Receive(RecvBytes, RECEIVE_SIZE, SocketFlags.None)
last_error = ""
return true




catch (System.Net.Sockets.SocketException ex

last_error = ex.Message
return false


last_error = "Timeout trying to reach the remote host"
return false


}