store.connect(imap.gmail.com, email, pass) can't connect to host, port imap.gmail.com, 993; timeout -1;

Question

I'm trying to create an app to send and receive emails, but whenever I run it in my emulator I get this error: System.err: com.sun.mail.util.MailConnectException: Couldn't connect to host, port: imap.gmail.com, 993; timeout -1; Using socket factory class javax.net.ssl.SSLSocketFactory;

I have checked my firewall and it doesn't block any ports as far as I can tell. This code is not in the main activity and the user email and password are transfered in extras. Any help would be appreciated.

private Adapter adapter = new Adapter(this);

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_main);

    final LinearLayout Activity_Email = findViewById(R.id.LinearLayout_ActivityEmail);
    final LinearLayout Activity_Main = findViewById(R.id.LinearLayout_ActivityMain);

    final Button Button_NewEmail = findViewById(R.id.Button_NewEmail);
    final Button Button_UserProfile = findViewById(R.id.Button_UserProfile);
    final Button Button_Contacts = findViewById(R.id.Button_Contacts);
    final Button Button_ProfileFolders = findViewById(R.id.Button_ProfileFolders);
    final Button Button_Settings = findViewById(R.id.Button_Settings);

    ListView ListView_Emails = findViewById(R.id.ListView_EmailList);
    final EditText EditText_Filter = findViewById(R.id.EditText_EmailFilter);

    final Bundle extras = getIntent().getExtras();

    Properties properties = System.getProperties();
    properties.put("mail.store.protocol", "imaps");
    properties.put("mail.imaps.port", "993");

    properties.setProperty("mail.imaps.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
    properties.setProperty("mail.imaps.socketFactory.fallback", "false");

    Session imapSession = Session.getInstance(properties);

    Thread thread = new Thread()
    {
        @Override
        public void run()
        {
            try {
                System.out.println("\nGetting store\n");
                Folder inbox;
                System.out.println("\nConnecting store\n");
                Store store = imapSession.getStore("imaps");
                System.out.println("\nGetting folder\n");

                store.connect("imap.gmail.com", extras.getString("USER_EMAIL"), extras.getString("PASSWORD"));
                inbox=store.getFolder("Inbox");

                inbox.open(Folder.READ_ONLY);
                Message messages[] = inbox.getMessages();
             
                int numberOfEmails = messages.length;
                for(int i = 0; i < numberOfEmails; i++)
                {
                    List_Email new_email = new List_Email(Arrays.toString(messages[i].getFrom()), extras.getString("USER_EMAIL"), messages[i].getSubject(), messages[i].getContent().toString());
                    adapter.addList_Email(new_email);
                }
            } catch (MessagingException e) {
                System.out.println("Prekid ovde Message\n");
                e.printStackTrace();
            } catch (IOException e) {
                System.out.println("Prekid ovde IO\n");
                e.printStackTrace();
            }
        }
    };
    thread.run();

    ListView_Emails.setAdapter(adapter);

    ListView_Emails.setOnItemClickListener(new MyOnItemClickListener());


    Button_NewEmail.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent intent = new Intent(Emails_Activity.this, NewEmailActivity.class);

            intent.putExtra("USER_EMAIL", extras.getString("USER_EMAIL"));
            intent.putExtra("PASSWORD", extras.getString("PASSWORD"));

            startActivity(intent);
        }
    });

    Button_ProfileFolders.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent intent = new Intent(Emails_Activity.this, FoldersActivity.class);
            startActivity(intent);
        }
    });
}

private class MyOnItemClickListener implements AdapterView.OnItemClickListener {

    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        Bundle extras =getIntent().getExtras();
        List_Email mail = (List_Email) adapter.getItem(position);
        Intent intent = new Intent(Emails_Activity.this, EmailActivity.class);

        String senderEmail = mail.Sender;
        String title = mail.Title;
        String content = mail.Content;

        intent.putExtra("Sender", senderEmail);
        intent.putExtra("Title", title);
        intent.putExtra("Content", content);

        startActivity(intent);
    }
}

}

In case it is needed, here is the AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.AUTHENTICATE_ACCOUNTS" />
<uses-permission android:name="android.permission.GET_ACCOUNTS" />
<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:roundIcon="@mipmap/ic_launcher_round"
    android:supportsRtl="true"
    android:theme="@style/Theme.MyEmailApp2">
    <activity android:name=".Emails_Activity">
    </activity>
    <activity android:name=".EmailActivity">
    </activity>
    <activity android:name=".NewEmailActivity">
    </activity>
    <activity android:name=".LoginActivity">
    </activity>
    <activity android:name=".FoldersActivity">
    </activity>
    <activity android:name=".MainActivity"
        android:exported="true">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

Here is the output in the Run tab when I get to the error while running the app on the emulator:

D/EGL_emulation: eglMakeCurrent: 0xda01a360: ver 3 1 (tinfo 0xda00f800)
I/chatty: uid=10135(com.example.myemailapp2) RenderThread identical 3 lines
D/EGL_emulation: eglMakeCurrent: 0xda01a360: ver 3 1 (tinfo 0xda00f800)
D/OpenGLRenderer: endAllActiveAnimators on 0xc299ab80 (RippleDrawable) with handle 0xda00fa50
D/EGL_emulation: eglMakeCurrent: 0xda01a360: ver 3 1 (tinfo 0xda00f800)
W/ActivityThread: handleWindowVisibility: no activity for token android.os.BinderProxy@8318084
I/System.out: Getting store
I/System.out: Connecting store
D/NetworkSecurityConfig: No Network Security Config specified, using platform default
I/System.out: Prekid ovde Message
W/System.err: com.sun.mail.util.MailConnectException: Couldn't connect to host, port: imap.gmail.com, 993; timeout -1; Using socket factory class javax.net.ssl.SSLSocketFactory;
  nested exception is:
    android.os.NetworkOnMainThreadException
W/System.err:     at com.sun.mail.imap.IMAPStore.protocolConnect(IMAPStore.java:735)
    at javax.mail.Service.connect(Service.java:366)
    at javax.mail.Service.connect(Service.java:246)
    at com.example.myemailapp2.Emails_Activity$1.run(Emails_Activity.java:79)
    at com.example.myemailapp2.Emails_Activity.onCreate(Emails_Activity.java:107)
    at android.app.Activity.performCreate(Activity.java:7802)
    at android.app.Activity.performCreate(Activity.java:7791)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1299)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3245)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409)
    at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
    at android.os.Handler.dispatchMessage(Handler.java:107)
    at android.os.Looper.loop(Looper.java:214)
    at android.app.ActivityThread.main(ActivityThread.java:7356)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
W/System.err: Caused by: android.os.NetworkOnMainThreadException
    at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1565)
    at java.net.Inet6AddressImpl.lookupHostByName(Inet6AddressImpl.java:115)
    at java.net.Inet6AddressImpl.lookupAllHostAddr(Inet6AddressImpl.java:103)
    at java.net.InetAddress.getByName(InetAddress.java:1106)
    at java.net.InetSocketAddress.<init>(InetSocketAddress.java:235)
    at com.sun.mail.util.SocketFetcher.createSocket(SocketFetcher.java:352)
    at com.sun.mail.util.SocketFetcher.getSocket(SocketFetcher.java:217)
    at com.sun.mail.iap.Protocol.<init>(Protocol.java:124)
    at com.sun.mail.imap.protocol.IMAPProtocol.<init>(IMAPProtocol.java:128)
    at com.sun.mail.imap.IMAPStore.newIMAPProtocol(IMAPStore.java:758)
    at com.sun.mail.imap.IMAPStore.protocolConnect(IMAPStore.java:693)
    ... 19 more
D/EGL_emulation: eglMakeCurrent: 0xda01a360: ver 3 1 (tinfo 0xda00f800)
D/EGL_emulation: eglMakeCurrent: 0xda01a360: ver 3 1 (tinfo 0xda00f800)

Answer 1

Your full stack trace shows the problem:

nested exception is:
    android.os.NetworkOnMainThreadException

You may not do any networking on the main thread of your android application. You must create a worker thread or similar and do it there.

The documentation for the NetworkOnMainThread exception further describes the problem and links to a document about why and how to deal with it.