Enable TCP Keepalive per application in Android using OkHttp

OkHttpUtils.java

import okhttp3.OkHttpClient;

public class OkHttpUtil {
    public static OkHttpClient getOkHttpClient() {
        return new OkHttpClient.Builder()
                .socketFactory(new TCPKeepaliveSocketFactory(60, 60, 5))
                .build();
    }

    public static OkHttpClient getSSLOkHttpClient() {
        return new OkHttpClient.Builder()
                .sslSocketFactory(new TCPKeepaliveSSLSocketFactory(getSSLSocketFactory(), 60, 60, 5), getX509TrustManager())
                .build();
    }
}

TCPKeepaliveSocketFactory.java

import java.io.IOException;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;

import javax.net.SocketFactory;

public class TCPKeepaliveSocketFactory extends SocketFactory {
    private final int idleTimeout;
    private final int interval;
    private final int count;

    public TCPKeepaliveSocketFactory(int idleTimeout, int interval, int count) {
        this.idleTimeout = idleTimeout;
        this.interval = interval;
        this.count = count;
    }

    @Override
    public Socket createSocket(String host, int port) throws IOException, UnknownHostException {
        Socket socket = new Socket(host, port);
        TCPKeepaliveSocketUtil.setTCPKeepAlive(socket, idleTimeout, interval, count);
        return socket;
    }

    @Override
    public Socket createSocket(String host, int port, InetAddress localHost, int localPort) throws IOException, UnknownHostException {
        Socket socket = new Socket(host, port, localHost, localPort);
        TCPKeepaliveSocketUtil.setTCPKeepAlive(socket, idleTimeout, interval, count);
        return socket;
    }

    @Override
    public Socket createSocket(InetAddress host, int port) throws IOException {
        Socket socket = new Socket(host, port);
        TCPKeepaliveSocketUtil.setTCPKeepAlive(socket, idleTimeout, interval, count);
        return socket;
    }

    @Override
    public Socket createSocket(InetAddress address, int port, InetAddress localAddress, int localPort) throws IOException {
        Socket socket = new Socket(address, port, localAddress, localPort);
        TCPKeepaliveSocketUtil.setTCPKeepAlive(socket, idleTimeout, interval, count);
        return socket;
    }
}

TCPKeepaliveSocketUtils.java

import android.system.Os;

import java.io.FileDescriptor;
import java.lang.reflect.Field;
import java.net.Socket;

public class TCPKeepaliveSocketUtil {
    /**
     * See https://www.iana.org/assignments/protocol-numbers/protocol-numbers.xhtml
     */
    private final static int SOL_TCP_LEVEL = 6;

    /**
     * See https://cs.android.com/android/platform/superproject/+/android-10.0.0_r30:bionic/libc/kernel/uapi/linux/tcp.h
     */
    private final static int TCP_KEEPIDLE_OPTION = 4;
    private final static int TCP_KEEPINTVL_OPTION = 5;
    private final static int TCP_KEEPCNT_OPTION = 6;

    /**
     * Enable and configure TCP Keep Alive on provided socket
     * Notice the socket should not be an SSLSocket as it's file descriptor will be unrecognisable by the OS
     * To use an SSLSocket, pass a normal socket to this function first, then construct an SSLSocket using the normal socket.
     *
     * @param socket Socket to be configured.
     * @param idleTimeout The interval between the last data packet sent (simple ACKs are not considered data) and the first keepalive probe in seconds
     * @param interval The interval between subsequential keepalive probes in seconds, regardless of what the connection has exchanged in the meantime
     * @param count The number of unacknowledged probes to send before considering the connection dead and notifying the application layer
     */
    @SuppressWarnings("JavaReflectionMemberAccess")
    public static void setTCPKeepAlive(Socket socket, int idleTimeout, int interval, int count) {
        try {
            socket.setKeepAlive(true);
            Field socketImplField = Class.forName("java.net.Socket").getDeclaredField("impl");
            if (socketImplField != null) {
                socketImplField.setAccessible(true);
                Object socketImpl = socketImplField.get(socket);
                Field fileDescriptorField = Class.forName("java.net.SocketImpl").getDeclaredField("fd");
                if (fileDescriptorField != null) {
                    fileDescriptorField.setAccessible(true);
                    final FileDescriptor fileDescriptor = (FileDescriptor) fileDescriptorField.get(socketImpl);
                    Os.setsockoptInt(fileDescriptor, SOL_TCP_LEVEL, TCP_KEEPIDLE_OPTION, idleTimeout);
                    Os.setsockoptInt(fileDescriptor, SOL_TCP_LEVEL, TCP_KEEPINTVL_OPTION, interval);
                    Os.setsockoptInt(fileDescriptor, SOL_TCP_LEVEL, TCP_KEEPCNT_OPTION, count);
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

TCPKeepaliveSSLSocketFactory.java

import java.io.IOException;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;

import javax.net.ssl.SSLSocketFactory;

public class TCPKeepaliveSSLSocketFactory extends SSLSocketFactory {
    private final SSLSocketFactory internalSSLSocketFactory;
    private int idleTimeout = 50;
    private int interval = 50;
    private int count = 3;

    public TCPKeepaliveSSLSocketFactory(SSLSocketFactory sslSocketFactory) {
        this.internalSSLSocketFactory = sslSocketFactory;
    }

    public TCPKeepaliveSSLSocketFactory(SSLSocketFactory sslSocketFactory, int idleTimeout, int interval, int count) {
        this.internalSSLSocketFactory = sslSocketFactory;
        this.idleTimeout = idleTimeout;
        this.interval = interval;
        this.count = count;
    }

    @Override
    public Socket createSocket(String host, int port) throws IOException, UnknownHostException {
        Socket socket = internalSSLSocketFactory.createSocket(host, port);
        TCPKeepaliveSocketUtil.setTCPKeepAlive(socket, idleTimeout, interval, count);
        return socket;
    }

    @Override
    public Socket createSocket(String host, int port, InetAddress localHost, int localPort) throws IOException, UnknownHostException {
        Socket socket = internalSSLSocketFactory.createSocket(host, port, localHost, localPort);
        TCPKeepaliveSocketUtil.setTCPKeepAlive(socket, idleTimeout, interval, count);
        return socket;
    }

    @Override
    public Socket createSocket(InetAddress host, int port) throws IOException {
        Socket socket = internalSSLSocketFactory.createSocket(host, port);
        TCPKeepaliveSocketUtil.setTCPKeepAlive(socket, idleTimeout, interval, count);
        return socket;
    }

    @Override
    public Socket createSocket(InetAddress address, int port, InetAddress localAddress, int localPort) throws IOException {
        Socket socket = internalSSLSocketFactory.createSocket(address, port, localAddress, localPort);
        TCPKeepaliveSocketUtil.setTCPKeepAlive(socket, idleTimeout, interval, count);
        return socket;
    }

    @Override
    public Socket createSocket(Socket s, String host, int port, boolean autoClose) throws IOException {
        TCPKeepaliveSocketUtil.setTCPKeepAlive(s, idleTimeout, interval, count); // Use underlying real socket to set TCP keep alive instead of wrapped SSLSocket
        return internalSSLSocketFactory.createSocket(s, host, port, autoClose);
    }

    @Override
    public String[] getDefaultCipherSuites() {
        return internalSSLSocketFactory.getDefaultCipherSuites();
    }

    @Override
    public String[] getSupportedCipherSuites() {
        return internalSSLSocketFactory.getSupportedCipherSuites();
    }
}

Based on this fantastic answer on StackOverflow, updated with new Android API and adapted to OkHttp
Tested working on both Android 9 and 10