JAVA: How to create http url connection selecting the ip address to use

Question

I have a pool of public ip addresses configured on my multiple NICs. In my JAVA project, which runs on a LINUX machine, I need to select a specific ip address from the pool and create an HttpURLConnecion using that ip. Further, I will cycle on the pool, using each time a different ip.

At the current stage, I was not able to find a solution using the java.net library. I have rather looked at the HttpClient from Apache. At the following link, http://hc.apache.org/httpcomponents-client-ga/tutorial/html/connmgmt.html, it is said that such library can support the functionality I was looking for. A discussion on this can be found at Define source ip address using Apache HttpClient. Actually, the posted thread seems not conclusive, as users' experiences are very contrasting on the described use of the library.

Therefore, I don't think that SO community really succeeded in solving this issue. It is a matter of fact that several replayed questions/answers on this topic can be found on SO, but none of them seems to give an exhaustive analysis of the problem.

Moreover, the problem is not faced with the use of java.net library (as in my project) at all.

At the moment, a possible option that I have is to invoke some LINUX system commands (from java) to switch the NIC to use for the current connection. However, I have not figure it out yet.

Therefore, I would appreciate if any users, who had POSITIVE experiences in solving this issue, can address me to a solution/idea/method.

Thanks in advance,

Marcello

UPDATE:

I've currently implemented this test code. It gives me correct status code (200). However, it needs to be tested with multiple ip addresses.

public class test {

    public static void main(String[] args) {

        final String authUser = "admin";
        final String authPassword = "password";
        Authenticator.setDefault(
           new Authenticator() {
              public PasswordAuthentication getPasswordAuthentication() {
                 return new PasswordAuthentication(
                       authUser, authPassword.toCharArray());
              }
           }
        );

        System.setProperty("http.proxyUser", authUser);
        System.setProperty("http.proxyPassword", authPassword);

        try {

            Properties systemProperties = System.getProperties();
            URL url = new URL("yourURL");
            systemProperties.setProperty("http.proxyHost","localhost");
            systemProperties.setProperty("http.proxyPort", "8080");                         

            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            int status = connection.getResponseCode();
            System.out.println(status);

        } catch (IOException e) {
            System.out.println("connection problems");
        }
    }

}

At this point, you should be able to configure the different TCP ports related to each NIC. Did anyone try something like this? I am looking forward to reading new ideas/comments.

UPDATE 2: To be precise, I've included authentication setup for those who needed it.

Solution

Why don't you just use org.apache.httpcomponents?

Here an example that works (using maven plugin org.apache.httpcomponents, version 4.3.1):

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.InetAddress;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.ResponseHandler;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;

public class HttpClientExample {

    public void gogo() throws ClientProtocolException, IOException {

        CloseableHttpClient httpclient = HttpClients.createDefault();

        // Local interface1:
        byte ip1[] = new byte[] { (byte)192, (byte)168, (byte)100, (byte)32 };
        // Local interface2:
        byte ip2[] = new byte[] { (byte)192, (byte)168, (byte)100, (byte)33 };


        RequestConfig requestConfig = RequestConfig.custom().setLocalAddress(InetAddress.getByAddress(ip1)).build();
        try {
            HttpGet httpget = new HttpGet("http://server.com");
            httpget.setConfig(requestConfig);
            System.out.println("executing request" + httpget.getRequestLine());
            StringBuilder response = httpclient.execute(httpget,handler);
            System.out.println(response.toString());

            requestConfig = RequestConfig.custom().setLocalAddress(InetAddress.getByAddress(ip2)).build();
            httpget = new HttpGet("http://server.com");
            httpget.setConfig(requestConfig);
            System.out.println("executing request" + httpget.getRequestLine());
            response = httpclient.execute(httpget,handler);
            System.out.println(response.toString());
        } finally {
            httpclient.close();
        }
    }

    private final ResponseHandler<StringBuilder> handler = new ResponseHandler<StringBuilder>() {
        @Override
        public StringBuilder handleResponse(final HttpResponse response)
                throws ClientProtocolException, IOException {
            return sortResponse(response);
        }
    };

    private StringBuilder sortResponse(final HttpResponse httpResponse) throws IOException {
        StringBuilder builder = null;

        if (httpResponse != null) {
            switch (httpResponse.getStatusLine().getStatusCode()) {
                case HttpStatus.SC_OK:
                    final HttpEntity entity = httpResponse.getEntity();
                    if (entity != null) {

                        final InputStreamReader instream = new InputStreamReader(entity.getContent());
                        try {
                            final BufferedReader reader = new BufferedReader(instream);
                            builder = new StringBuilder();
                            String currentLine = null;
                            currentLine = reader.readLine();
                            while (currentLine != null) {
                                builder.append(currentLine).append("\n");
                                currentLine = reader.readLine();
                            }
                        } finally {
                            instream.close();
                        }
                    }
                    break;
                default:
                    throw new IllegalArgumentException("Error.");
            }
        }
        return builder;
    }
}

Comments

[m121212]

Hi. I've just implemented this method, and it does not work. Anyway, the proxy type should be HTTP and the connection a HttpURLConnection type. However, the proxy configuration does not work. When I try to establish normal connection without proxy usage, everything works fine. Therefore, the issue is still OPEN!

[m121212]

Thanks for the suggestion. Can you provide me some basic code example, or is it just a try?

[Kishan Bheemajiyani]

Means issue about what you are trying to specify the particular address is that?? and then put that address as if default address then try to run again na.. try that once and ya even i am confuse about this thing its not working it. i am also working on same.

[Gooseman]

@Krishna Right, it sends the same HTTP request using 2 different local interfaces (NICs). In my example eth0 could be 192.168.100.32 and eth1 192.168.100.33. Socket.bind() enables you to send data by means of your chosen local address (NIC) and not the one chosen by the system.

[m121212]

Thank you. I know that this is nicely handled with Apache library, but I'm trying to find a solution that works with native java.net.

[Gooseman]

@m121212 You are welcome. I left this code for you just in case you finally give up trying to use java.net. :P

[Sep GH]

Guess it's not byte ip1[] , but byte[] ip , right? and thanks for the solution! still cant find good answer in SO community that uses only native java.net!

[Gooseman]

@SepehrGH byte ip1[] is also right. See: JLS §10.2

[Sep GH]

oh! I see, tnx for the link

[Sep GH]

Sorry to bother. I'm testing this code on my machine which is connected to internet using both LAN and WIFI. wlp3s0 has inet address: 192.168.1.6 , and enp4s0f1 has 192.168.1.4 assigned to it (which should probably be my lan address). I can run this code when I set ip to enp4s0f1 one (192.168.1.4) but doesnt work when I change to wifi one! can this be a valid test? I want to make sure when I run my app on server with multiple addresses, it works fine.

[Nathan B]

doesn't work for me. Says: java.net.BindException: Cannot assign requested address (Bind failed)

[Gooseman]

@NathanB Bind failed is due to some of these problems: EADDRINUSE, EADDRNOTAVAIL, EPERM or EACCES. For openjdk8 you can see the related code over here. If you are using Linux, the command man bind will explain you what those code errors mean.

[Gooseman]

Sorry @SepGH. I never saw your latest question until now. It should have worked also with the wifi interface.