communication between android and pc #587

pablo-souza · 2021-12-27T18:02:06Z

pablo-souza
Dec 27, 2021

I'm trying to create a connection between an Android application and another one on the PC.
In some moments it is listed that the mebro mobile (app) joined the group, but they do not exchange messages. They always end up in two different groups.
Are there any examples to follow? something "piece of cake"?

My current code:

package infra;
import android.util.Log;

import org.jgroups.JChannel;
import org.jgroups.Message;
import org.jgroups.ObjectMessage;
import org.jgroups.Receiver;
import org.jgroups.View;
import org.jgroups.protocols.*;
import org.jgroups.protocols.pbcast.GMS;
import org.jgroups.protocols.pbcast.NAKACK2;
import org.jgroups.protocols.pbcast.STABLE;
import org.jgroups.protocols.pbcast.STATE_TRANSFER;
import org.jgroups.stack.IpAddress;
import org.jgroups.stack.Protocol;
import org.jgroups.util.Util;

import java.io.*;
import java.net.InetAddress;
import java.util.List;
import java.util.LinkedList;

import io.flutter.plugin.common.MethodChannel;

public class Cluster implements Receiver {
    
    JChannel channelCluster;
    String user_name=System.getProperty("user.name", "n/a");
    final List<String> state=new LinkedList<>();
    
    public void viewAccepted(View new_view) {
        Log.d("view","** view: " + new_view);
    }

    public void receive(Message msg) {
        String line=msg.getSrc() + ": " + msg.getObject();
        System.out.println(line);
        synchronized(state) {
            state.add(line);
        }
    }

    public void getState(OutputStream output) throws Exception {
        synchronized(state) {
            Util.objectToStream(state, new DataOutputStream(output));
        }
    }

    @SuppressWarnings("unchecked")
    public void setState(InputStream input) throws Exception {
        List<String> list=Util.objectFromStream(new DataInputStream(input));
        synchronized(state) {
            state.clear();
            state.addAll(list);
        }
        Log.d("recebido","received state (" + list.size() + " messages in chat history):");
        list.forEach(System.out::println);
    }

    public void start(String canal,String ip) throws Exception {
        Protocol[] prot_stack={
                new UDP()
                        .setValue("bind_addr", InetAddress.getByName(ip))
                        .setValue("mcast_addr", new IpAddress("192.168.42.255") )
                        .setValue("mcast_port",45588)
                        .setValue("ip_ttl",4)
                        .setValue("ucast_recv_buf_size",210)
                        .setValue("ucast_send_buf_size",210)
                        .setValue("mcast_recv_buf_size",210)
                        .setValue("mcast_send_buf_size",210)
                        .setValue("max_bundle_size",64)
                        .setValue("enable_diagnostics",true)
                        .setValue("thread_naming_pattern","cl"),
                new PING(),
                new MERGE3()
                        .setValue("max_interval",30000)
                        .setValue("max_interval",10000),
                new FD_SOCK(),
                new FD_ALL(),
                new BARRIER(),
                new NAKACK2()
                        .setValue("xmit_interval",500)
                        .setValue("xmit_table_num_rows",100)
                        .setValue("xmit_table_msgs_per_row",2000)
                        .setValue("xmit_table_max_compaction_time",30000),
                new UNICAST3()
                        .setValue("xmit_interval",500)
                        .setValue("xmit_table_num_rows",100)
                        .setValue("xmit_table_msgs_per_row",2000)
                        .setValue("xmit_table_max_compaction_time",60000),
                new STABLE()
                        .setValue("desired_avg_gossip",5000)
                        .setValue("max_bytes",40000),
                new GMS()
                        .setValue("print_local_addr",false)
                        .setValue("join_timeout", 5000),
                new UFC()
                        .setValue("max_credits",2000)
                        .setValue("min_threshold",0.4),
                new MFC()
                        .setValue("max_credits",2000)
                        .setValue("min_threshold",0.4),
                new FRAG2()
                        .setValue("frag_size",60),
                new RSVP(),
                new STATE_TRANSFER()
        };
        channelCluster =new JChannel(prot_stack);
        channelCluster.setReceiver(this);
        channelCluster.setName("PDV-Mobile");
        channelCluster.connect("ChatCluster");
        Log.d("ChatCluster","iniciado");
        channelCluster.getState(null, 10000);
        String msgString = Math.random()+"";
        Message msg = new ObjectMessage(null,msgString);
        channelCluster.send(msg);
//        channelCluster.close();
    }



}

belaban · 2021-12-28T18:13:41Z

belaban
Dec 28, 2021
Maintainer

mcast_addr of 192.168.42.255 is not a valid class D address. Also, if you want to use a correct bind_addr, both devices need to have a route from the bind_addr to the given mcast_addr. If you communicate between a PC and an Android phone, then both need to be connected to the wireless network. So make sure you pick bind_addr and mcast_addr correctly.
Besides this, the receive/send buffers are very small (210 bytes): is this by intention?

1 reply

pablo-souza Dec 29, 2021
Author

new TCP()
        .setValue("bind_addr", InetAddress.getByName(ip))
        .setValue("bind_port",45588),
new TCPPING()
        .setValue("initial_hosts",ips),

I changed the connection to TCP in order to test, and it worked perfectly.
But I have to use UDP, but Android is always disconnecting...
He finds the group, sends a message and then splits into two subgroups that you never talk to...

** view: MergeView::[PDV-Mobile|43] (2) [PDV-Mobile, PC - 0.21306954210095574], 2 subgroups: [PDV-Mobile|42] (1) [PDV-Mobile], [PDV-Mobile|41] (2) [PDV-Mobile, PC - 0.21306954210095574]
** view: PDV-Mobile
** view: PC - 0.21306954210095574
dez 29, 2021 4:49:21 PM org.jgroups.protocols.pbcast.GMS castViewChangeAndSendJoinRsps
ADVERTÊNCIA: PC - 0.21306954210095574: failed to collect all ACKs (expected=1) for view [PDV-Mobile|43] after 2001 ms, missing 1 ACKs from (1) PDV-Mobile

How should I make the settings?

new UDP()
        .setValue("bind_addr", InetAddress.getByName("192.168.42.16"))
        .setValue("", new IpAddress("228.8.8.8") )
        .setValue("mcast_port",45588)
        .setValue("ip_ttl",4)
        .setValue("ucast_recv_buf_size",1024)
        .setValue("ucast_send_buf_size",1024)
        .setValue("mcast_recv_buf_size",1024)
        .setValue("mcast_send_buf_size",1024)
        .setValue("max_bundle_size",64)
        .setValue("enable_diagnostics",true)
        .setValue("thread_naming_pattern","cl"),
new PING(),

belaban · 2021-12-30T11:04:50Z

belaban
Dec 30, 2021
Maintainer

Use probe.sh to find out which failure detection protocol caused the split. I suspect it could be FD_SOCK, perhaps look at bind_addr there, too.
If TCP works, but UDP doesn't, that shows that your network might not be configured correctly. Check routing tables (mcast route for 240.0.0.0?),firewalls etc. Or use nc -u{s,c} or iperf to test your network...

0 replies

pablo-souza · 2022-01-03T15:59:03Z

pablo-souza
Jan 3, 2022
Author

As instructed, I ran the tests, but I don't know what to look for in the results, could you help me with that?.
But some things caught my attention:

FD_SOCK->ping_dest=PDV-Mobile, // I thought there was no communication
GMS->"view=MergeView"::[
      PC - 0.10759923973275332|60
   ](2)[
      PC - 0.10759923973275332,
      "PDV-Mobile"
   ],
   "2 subgroups":[
      PC - 0.10759923973275332|58
   ](2)[
      PC - 0.10759923973275332,
      "PDV-Mobile"
   ],
   [
      PDV-Mobile|59
   ](1)[
      "PDV-Mobile"
   ],

It doesn't seem right to me
iperf result:

iperf -c 192.168.47.16 -i1 -t60 -u
------------------------------------------------------------
Client connecting to 192.168.47.16, UDP port 5001
Sending 1470 byte datagrams, IPG target: 11215.21 us (kalman adjust)
UDP buffer size:  208 KByte (default)
------------------------------------------------------------
[  3] local 192.168.42.16 port 39182 connected with 192.168.47.16 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0- 1.0 sec   131 KBytes  1.07 Mbits/sec
[  3]  1.0- 2.0 sec   128 KBytes  1.05 Mbits/sec
[  3]  2.0- 3.0 sec   128 KBytes  1.05 Mbits/sec
						.
						.
						.
[  3] WARNING: did not receive ack of last datagram after 10 tries.
[  3]  0.0-60.0 sec  7.50 MBytes  1.05 Mbits/sec
[  3] Sent 5350 datagram

this is what happens as soon as i run the Android app with the PC running:

** view: [PC - 0.8254817004934131|15] (1) [PC - 0.8254817004934131]
** view: [PC - 0.8254817004934131|16] (2) [PC - 0.8254817004934131, PDV-Mobile]
PDV-Mobile: 0.3893695810204203

then run:

input: test

Result:

PC - 0.8254817004934131: [pablo] test
jan 03, 2022 11:41:02 AM org.jgroups.protocols.pbcast.GMS installView
ADVERTÊNCIA: PC - 0.8254817004934131: not member of view [PDV-Mobile|17]; discarding it

and after a while it starts to happen:

** view: MergeView::[PC - 0.8254817004934131|20] (2) [PC - 0.8254817004934131, PDV-Mobile], 2 subgroups: [PDV-Mobile|19] (1) [PDV-Mobile], [PC - 0.8254817004934131|18] (2) [PC - 0.8254817004934131, PDV-Mobile]
** Membro view: PC - 0.8254817004934131
** Membro view: PDV-Mobile
jan 03, 2022 11:42:15 AM org.jgroups.protocols.pbcast.GMS castViewChangeAndSendJoinRsps
ADVERTÊNCIA: PC - 0.8254817004934131: failed to collect all ACKs (expected=1) for view [PC - 0.8254817004934131|20] after 2007 ms, missing 1 ACKs from (1) PDV-Mobile
jan 03, 2022 11:42:53 AM org.jgroups.protocols.pbcast.GMS installView
ADVERTÊNCIA: PC - 0.8254817004934131: not member of view [PDV-Mobile|21]; discarding it

6 replies

belaban Jan 3, 2022
Maintainer

Seems like the mobile (PDV-Mobile) device suspects and excludes the PC. Run probe.sh jmx=FD_SOCK.num_sus to see how many suspect events each member has

belaban Jan 3, 2022
Maintainer

Also, there are 60 views... I guess PC gets excluded, then merges again with mobile, gets excluded again etc...

pablo-souza Jan 3, 2022
Author

How do I use the probe to check Android App?

pablo-souza Jan 3, 2022
Author

Even with the errors, the result was this
PC result:

Probe jmx=FD_SOCK.num_sus
#1 (190 bytes):
local_addr=PC - 0.30378800512373616 [ip=192.168.42.16:43948, version=5.0.0.Final (Stelvio), cluster=ChatCluster, 2 mbr(s)]
FD_SOCK={num_suspect_events_generated=0, num_suspected_members=0}

pablo-souza Jan 3, 2022
Author

Android OS may be terminating connections?

belaban · 2022-01-03T18:26:58Z

belaban
Jan 3, 2022
Maintainer

OK, good, so this shows that FD_SOCK on PC did not suspect the Mobile device. IIRC, it was the other way round... Also run the same wih FD_ALL or FD_ALL2, or whichever protocol you use...
And run it with FD_SOCK and FD_ALL on the Mobile.

0 replies

belaban · 2022-01-03T18:28:22Z

belaban
Jan 3, 2022
Maintainer

You can run probe directly connecting to mobile: probe.sh -addr (-udp true -tcp false)

2 replies

pablo-souza Jan 3, 2022
Author

command complete is Probe -addr 192.168.42.67 -udp true -tcp false?

pablo-souza Jan 3, 2022
Author

Result: 0 responses (0 matches, 0 non matches)

belaban · 2022-01-03T18:28:51Z

belaban
Jan 3, 2022
Maintainer

Or try nc -u <addr of mobile) 7500

0 replies

pablo-souza · 2022-01-04T13:05:49Z

pablo-souza
Jan 4, 2022
Author

I updated the version of jgroups from 5.0.0 to 5.1.7 and now I was able to connect to the Mobile application, however this happens:
nc -u 192.168.42.67 7500
probe jmx=FD_SOCK
out:

JGRP000235: failure handling diagnostics request
    java.lang.NoClassDefFoundError: Failed resolution of: Ljavax/management/DynamicMBean;
        at org.jgroups.stack.ProtocolStack.dumpStats(ProtocolStack.java:399)
        at org.jgroups.stack.ProtocolStack.dumpStats(ProtocolStack.java:292)
        at org.jgroups.JChannel.dumpStats(JChannel.java:305)
        at org.jgroups.JChannelProbeHandler.dumpAttrsSelectedProtocol(JChannelProbeHandler.java:223)
        at org.jgroups.JChannelProbeHandler.handleJmx(JChannelProbeHandler.java:238)
        at org.jgroups.JChannelProbeHandler.handleProbe(JChannelProbeHandler.java:38)
        at org.jgroups.stack.DiagnosticsHandler.handleDiagnosticProbe(DiagnosticsHandler.java:260)
        at org.jgroups.stack.DiagnosticsHandler.runUDP(DiagnosticsHandler.java:145)
        at org.jgroups.stack.DiagnosticsHandler$$ExternalSyntheticLambda3.run(Unknown Source:2)
        at org.jgroups.util.Runner.run(Runner.java:75)
        at java.lang.Thread.run(Thread.java:764)
     Caused by: java.lang.ClassNotFoundException: Didn't find class "javax.management.DynamicMBean" on path: DexPathList[[zip file "/data/app/br.com.moura.pdvmobile.pdvmobile-VXfv8k7cPwDwN22ad1bndg==/base.apk"],nativeLibraryDirectories=[/data/app/br.com.moura.pdvmobile.pdvmobile-VXfv8k7cPwDwN22ad1bndg==/lib/x86, /data/app/br.com.moura.pdvmobile.pdvmobile-VXfv8k7cPwDwN22ad1bndg==/base.apk!/lib/x86, /system/lib, /system/vendor/lib]]
        at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:125)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:379)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
        at org.jgroups.stack.ProtocolStack.dumpStats(ProtocolStack.java:399) 
        at org.jgroups.stack.ProtocolStack.dumpStats(ProtocolStack.java:292) 
        at org.jgroups.JChannel.dumpStats(JChannel.java:305) 
        at org.jgroups.JChannelProbeHandler.dumpAttrsSelectedProtocol(JChannelProbeHandler.java:223) 
        at org.jgroups.JChannelProbeHandler.handleJmx(JChannelProbeHandler.java:238) 
        at org.jgroups.JChannelProbeHandler.handleProbe(JChannelProbeHandler.java:38) 
        at org.jgroups.stack.DiagnosticsHandler.handleDiagnosticProbe(DiagnosticsHandler.java:260) 
        at org.jgroups.stack.DiagnosticsHandler.runUDP(DiagnosticsHandler.java:145) 
        at org.jgroups.stack.DiagnosticsHandler$$ExternalSyntheticLambda3.run(Unknown Source:2) 
        at org.jgroups.util.Runner.run(Runner.java:75) 
        at java.lang.Thread.run(Thread.java:764)

Probe -addr 192.168.42.67 -udp true jmx=FD_SOCK
out:

JGRP000235: failure handling diagnostics request
    java.lang.NoClassDefFoundError: Failed resolution of: Ljavax/management/DynamicMBean;
        at org.jgroups.stack.ProtocolStack.dumpStats(ProtocolStack.java:399)
        at org.jgroups.stack.ProtocolStack.dumpStats(ProtocolStack.java:292)
        at org.jgroups.JChannel.dumpStats(JChannel.java:305)
        at org.jgroups.JChannelProbeHandler.dumpAttrsSelectedProtocol(JChannelProbeHandler.java:223)
        at org.jgroups.JChannelProbeHandler.handleJmx(JChannelProbeHandler.java:238)
        at org.jgroups.JChannelProbeHandler.handleProbe(JChannelProbeHandler.java:38)
        at org.jgroups.stack.DiagnosticsHandler.handleDiagnosticProbe(DiagnosticsHandler.java:260)
        at org.jgroups.stack.DiagnosticsHandler.runUDP(DiagnosticsHandler.java:145)
        at org.jgroups.stack.DiagnosticsHandler$$ExternalSyntheticLambda3.run(Unknown Source:2)
        at org.jgroups.util.Runner.run(Runner.java:75)
        at java.lang.Thread.run(Thread.java:764)
     Caused by: java.lang.ClassNotFoundException: Didn't find class "javax.management.DynamicMBean" on path: DexPathList[[zip file "/data/app/br.com.moura.pdvmobile.pdvmobile-VXfv8k7cPwDwN22ad1bndg==/base.apk"],nativeLibraryDirectories=[/data/app/br.com.moura.pdvmobile.pdvmobile-VXfv8k7cPwDwN22ad1bndg==/lib/x86, /data/app/br.com.moura.pdvmobile.pdvmobile-VXfv8k7cPwDwN22ad1bndg==/base.apk!/lib/x86, /system/lib, /system/vendor/lib]]
        at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:125)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:379)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
        at org.jgroups.stack.ProtocolStack.dumpStats(ProtocolStack.java:399) 
        at org.jgroups.stack.ProtocolStack.dumpStats(ProtocolStack.java:292) 
        at org.jgroups.JChannel.dumpStats(JChannel.java:305) 
        at org.jgroups.JChannelProbeHandler.dumpAttrsSelectedProtocol(JChannelProbeHandler.java:223) 
        at org.jgroups.JChannelProbeHandler.handleJmx(JChannelProbeHandler.java:238) 
        at org.jgroups.JChannelProbeHandler.handleProbe(JChannelProbeHandler.java:38) 
        at org.jgroups.stack.DiagnosticsHandler.handleDiagnosticProbe(DiagnosticsHandler.java:260) 
        at org.jgroups.stack.DiagnosticsHandler.runUDP(DiagnosticsHandler.java:145) 
        at org.jgroups.stack.DiagnosticsHandler$$ExternalSyntheticLambda3.run(Unknown Source:2) 
        at org.jgroups.util.Runner.run(Runner.java:75) 
        at java.lang.Thread.run(Thread.java:764)

Am I doing something wrong?

3 replies

belaban Jan 4, 2022
Maintainer

Looks like Android doesn't have support for JMX... I'm not an expert, so I don't know.

pablo-souza Jan 4, 2022
Author

According to this topic, you are right:
javax.* cannot be imported in my Android app?

Be aware that when you run an Android app: you don't run/compile it on a standard JVM/JDK, you don't even execute java bytecode. Google choose the java language (or at least a subset of it) as the language to do Android development, but it's only the language.

At the end the compiled java code is not java bytecode, but this is dalvik bytecode. (there is no .class files, but .dex files)

So, when doing Android development: you cannot use the full JavaSE API: you are limited to the API supported by the dalvik VM (available here).

(Note that when you browse this API beware of the version in the top right corner of the page : Added in API level X. It informs you about the Android-API version supporting that class or method)

Would you have any suggestions on how to debug the application? suggestion where to place the breakpoints?

belaban Jan 6, 2022
Maintainer

OK, so you can disable diagnostics altogether... Not a good idea, but perhaps you can use the same procedure as in ProgrammaticChat:

DiagnosticsHandler diag_handler=transport.getDiagnosticsHandler();
if(diag_handler != null) {
    Set<DiagnosticsHandler.ProbeHandler> probe_handlers=diag_handler.getProbeHandlers();
    probe_handlers.removeIf(probe_handler -> {
        String[] keys=probe_handler.supportedKeys();
         return keys != null && Stream.of(keys).anyMatch(s -> s.startsWith("jmx"));
     });
}
h=new NonReflectiveProbeHandler(ch).initialize(ch.getProtocolStack().getProtocols());
transport.registerProbeHandler(h);

This does not use JMX at all

pablo-souza · 2022-01-06T14:11:24Z

pablo-souza
Jan 6, 2022
Author

I would like to thank you for your attention and help, I am sorry for not being able to make Jgroups work via UDP, but at least it worked via TCP.
I believe that in theory it is possible to encapsulate a UDP process written outside the library, to simulate what would be normal behavior inside Jgroups...
I didn't get to do this, but it's an idea for someone in the future

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communication between android and pc #587

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communication between android and pc #587

pablo-souza Dec 27, 2021

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