CODEWITHSUNDEEP
javanetwork-programmingping
Keir Nellyer
Keir Nellyer

Reputation: 923

Thread safe InetAddress.isReachable()

In my Java application I need to get the ping of multiple connections at once, I have tried using a thread for each connection and measuring the response time but they don't all seem to be correct.

Is there a thread safe way to measure the ping/response time of a connection? I am currently using:

Thread thread = new Thread(new Runnable() {
    public void run(){
        long start = System.currentTimeMillis();
        someInetAddress.isReachable(5000);
        long timeTaken = System.currentTimeMillis() - start;
    }
});

However timeTaken doesn't seem to be correct as users with 150 ping are getting 5000 (probably more because it seems to have timed out)

Help is appreciated! Keir

Edit: Okay found out that its due to Port 7 being closed for some people, is there any other way to ping them without them having to have Port 7 closed?

Upvotes: 0

Views: 876

Answers (1)

user207421
user207421

Reputation: 311039

The isReachable() method works by trying to connect to TCP port 7 (echo). It doens't actually care whether port 7 is closed or not. All it cares about is whether there is a response of any kind to the connect. A ConnectException rates as isReachable = true, and it should take about the same amount of time as a successful connection, maybe even quicker. A connect timeout, host not reachable, etc, rate as false.

The method is advertised to use ICMP in very limited circumstances: you aren't on Windows and you have root privilege. In practice this never applies.

Upvotes: 1

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