Make a setting for WS

app/src/main/java/io/heckel/ntfy/data/Repository.kt

@@ -189,6 +189,22 @@ class Repository(private val sharedPrefs: SharedPreferences, private val subscri
             .apply()
     }
 
+    fun setConnectionProtocol(connectionProtocol: String) {
+        if (connectionProtocol == CONNECTION_PROTOCOL_JSONHTTP) {
+            sharedPrefs.edit()
+                .remove(SHARED_PREFS_CONNECTION_PROTOCOL)
+                .apply()
+        } else {
+            sharedPrefs.edit()
+                .putString(SHARED_PREFS_CONNECTION_PROTOCOL, connectionProtocol)
+                .apply()
+        }
+    }
+
+    fun getConnectionProtocol(): String {
+        return sharedPrefs.getString(SHARED_PREFS_CONNECTION_PROTOCOL, null) ?: CONNECTION_PROTOCOL_JSONHTTP
+    }
+
     fun getBroadcastEnabled(): Boolean {
         return sharedPrefs.getBoolean(SHARED_PREFS_BROADCAST_ENABLED, true) // Enabled by default
     }
@@ -321,6 +337,7 @@ class Repository(private val sharedPrefs: SharedPreferences, private val subscri
         const val SHARED_PREFS_MIN_PRIORITY = "MinPriority"
         const val SHARED_PREFS_AUTO_DOWNLOAD_MAX_SIZE = "AutoDownload"
         const val SHARED_PREFS_WAKELOCK_ENABLED = "WakelockEnabled"
+        const val SHARED_PREFS_CONNECTION_PROTOCOL = "ConnectionProtocol"
         const val SHARED_PREFS_BROADCAST_ENABLED = "BroadcastEnabled"
         const val SHARED_PREFS_UNIFIED_PUSH_ENABLED = "UnifiedPushEnabled"
         const val SHARED_PREFS_UNIFIED_PUSH_BASE_URL = "UnifiedPushBaseURL"
@@ -329,6 +346,9 @@ class Repository(private val sharedPrefs: SharedPreferences, private val subscri
         const val AUTO_DOWNLOAD_ALWAYS = 1L
         const val AUTO_DOWNLOAD_DEFAULT = 1024 * 1024L // Must match a value in values.xml
 
+        const val CONNECTION_PROTOCOL_JSONHTTP = "jsonhttp"
+        const val CONNECTION_PROTOCOL_WS = "ws"
+
         private const val TAG = "NtfyRepository"
         private var instance: Repository? = null
 

app/src/main/java/io/heckel/ntfy/msg/ApiService.kt

@@ -2,12 +2,8 @@ package io.heckel.ntfy.msg
 
 import android.os.Build
 import android.util.Log
-import androidx.annotation.Keep
-import com.google.gson.Gson
 import io.heckel.ntfy.BuildConfig
-import io.heckel.ntfy.data.Attachment
 import io.heckel.ntfy.data.Notification
-import io.heckel.ntfy.data.PROGRESS_NONE
 import io.heckel.ntfy.util.*
 import okhttp3.*
 import okhttp3.RequestBody.Companion.toRequestBody
@@ -16,7 +12,6 @@ import java.util.concurrent.TimeUnit
 import kotlin.random.Random
 
 class ApiService {
-    private val gson = Gson()
     private val client = OkHttpClient.Builder()
         .callTimeout(15, TimeUnit.SECONDS) // Total timeout for entire request
         .connectTimeout(15, TimeUnit.SECONDS)
@@ -26,6 +21,7 @@ class ApiService {
     private val subscriberClient = OkHttpClient.Builder()
         .readTimeout(5, TimeUnit.MINUTES) // Assuming that keepalive messages are more frequent than this
         .build()
+    private val parser = NotificationParser()
 
     fun publish(baseUrl: String, topic: String, message: String, title: String, priority: Int, tags: List<String>, delay: String) {
         val url = topicUrl(baseUrl, topic)
@@ -70,9 +66,10 @@ class ApiService {
             }
             val body = response.body?.string()?.trim()
             if (body == null || body.isEmpty()) return emptyList()
-            val notifications = body.lines().map { line ->
+            val notifications = body.lines().mapNotNull { line ->
-                fromString(subscriptionId, line)
+                parser.parse(line, subscriptionId = subscriptionId, notificationId = 0) // No notification when we poll
             }
+
             Log.d(TAG, "Notifications: $notifications")
             return notifications
         }
@@ -103,32 +100,9 @@ class ApiService {
                     val source = response.body?.source() ?: throw Exception("Unexpected response for $url: body is empty")
                     while (!source.exhausted()) {
                         val line = source.readUtf8Line() ?: throw Exception("Unexpected response for $url: line is null")
-                        val message = gson.fromJson(line, Message::class.java)
+                        val notification = parser.parseWithTopic(line, notificationId = Random.nextInt(), subscriptionId = 0) // subscriptionId to be set downstream
-                        if (message.event == EVENT_MESSAGE) {
+                        if (notification != null) {
-                            val topic = message.topic
+                            notify(notification.topic, notification.notification)
-                            val attachment = if (message.attachment?.url != null) {
-                                Attachment(
-                                    name = message.attachment.name,
-                                    type = message.attachment.type,
-                                    size = message.attachment.size,
-                                    expires = message.attachment.expires,
-                                    url = message.attachment.url,
-                                )
-                            } else null
-                            val notification = Notification(
-                                id = message.id,
-                                subscriptionId = 0, // TO BE SET downstream
-                                timestamp = message.time,
-                                title = message.title ?: "",
-                                message = message.message,
-                                priority = toPriority(message.priority),
-                                tags = joinTags(message.tags),
-                                click = message.click ?: "",
-                                attachment = attachment,
-                                notificationId = Random.nextInt(),
-                                deleted = false
-                            )
-                            notify(topic, notification)
                         }
                     }
                 } catch (e: Exception) {
@@ -144,57 +118,6 @@ class ApiService {
         return call
     }
 
-    private fun fromString(subscriptionId: Long, s: String): Notification {
-        val message = gson.fromJson(s, Message::class.java)
-        val attachment = if (message.attachment?.url != null) {
-            Attachment(
-                name = message.attachment.name,
-                type = message.attachment.type,
-                size = message.attachment.size,
-                expires = message.attachment.expires,
-                url = message.attachment.url,
-            )
-        } else null
-        return Notification(
-            id = message.id,
-            subscriptionId = subscriptionId,
-            timestamp = message.time,
-            title = message.title ?: "",
-            message = message.message,
-            priority = toPriority(message.priority),
-            tags = joinTags(message.tags),
-            click = message.click ?: "",
-            attachment = attachment,
-            notificationId = 0, // zero: when we poll, we do not want a notificationId!
-            deleted = false
-        )
-    }
-
-    /* This annotation ensures that proguard still works in production builds,
-     * see https://stackoverflow.com/a/62753300/1440785 */
-    @Keep
-    data class Message(
-        val id: String,
-        val time: Long,
-        val event: String,
-        val topic: String,
-        val priority: Int?,
-        val tags: List<String>?,
-        val click: String?,
-        val title: String?,
-        val message: String,
-        val attachment: MessageAttachment?,
-    )
-
-    @Keep
-    data class MessageAttachment(
-        val name: String,
-        val type: String?,
-        val size: Long?,
-        val expires: Long?,
-        val url: String,
-    )
-
     companion object {
         val USER_AGENT = "ntfy/${BuildConfig.VERSION_NAME} (${BuildConfig.FLAVOR}; Android ${Build.VERSION.RELEASE}; SDK ${Build.VERSION.SDK_INT})"
         private const val TAG = "NtfyApiService"

app/src/main/java/io/heckel/ntfy/msg/Message.kt

@@ -0,0 +1,28 @@
+package io.heckel.ntfy.msg
+
+import androidx.annotation.Keep
+
+/* This annotation ensures that proguard still works in production builds,
+ * see https://stackoverflow.com/a/62753300/1440785 */
+@Keep
+data class Message(
+    val id: String,
+    val time: Long,
+    val event: String,
+    val topic: String,
+    val priority: Int?,
+    val tags: List<String>?,
+    val click: String?,
+    val title: String?,
+    val message: String,
+    val attachment: MessageAttachment?,
+)
+
+@Keep
+data class MessageAttachment(
+    val name: String,
+    val type: String?,
+    val size: Long?,
+    val expires: Long?,
+    val url: String,
+)

app/src/main/java/io/heckel/ntfy/msg/NotificationParser.kt

@@ -0,0 +1,48 @@
+package io.heckel.ntfy.msg
+
+import com.google.gson.Gson
+import io.heckel.ntfy.data.Attachment
+import io.heckel.ntfy.data.Notification
+import io.heckel.ntfy.util.joinTags
+import io.heckel.ntfy.util.toPriority
+
+class NotificationParser {
+    private val gson = Gson()
+
+    fun parse(s: String, subscriptionId: Long = 0, notificationId: Int = 0): Notification? {
+        val notificationWithTopic = parseWithTopic(s, subscriptionId = subscriptionId, notificationId = notificationId)
+        return notificationWithTopic?.notification
+    }
+
+    fun parseWithTopic(s: String, subscriptionId: Long = 0, notificationId: Int = 0): NotificationWithTopic? {
+        val message = gson.fromJson(s, Message::class.java)
+        if (message.event != ApiService.EVENT_MESSAGE) {
+            return null
+        }
+        val attachment = if (message.attachment?.url != null) {
+            Attachment(
+                name = message.attachment.name,
+                type = message.attachment.type,
+                size = message.attachment.size,
+                expires = message.attachment.expires,
+                url = message.attachment.url,
+            )
+        } else null
+        val notification = Notification(
+            id = message.id,
+            subscriptionId = subscriptionId,
+            timestamp = message.time,
+            title = message.title ?: "",
+            message = message.message,
+            priority = toPriority(message.priority),
+            tags = joinTags(message.tags),
+            click = message.click ?: "",
+            attachment = attachment,
+            notificationId = notificationId,
+            deleted = false
+        )
+        return NotificationWithTopic(message.topic, notification)
+    }
+
+    data class NotificationWithTopic(val topic: String, val notification: Notification)
+}

app/src/main/java/io/heckel/ntfy/service/SubscriberService.kt

@@ -15,6 +15,7 @@ import io.heckel.ntfy.BuildConfig
 import io.heckel.ntfy.R
 import io.heckel.ntfy.app.Application
 import io.heckel.ntfy.data.ConnectionState
+import io.heckel.ntfy.data.Repository
 import io.heckel.ntfy.data.Subscription
 import io.heckel.ntfy.msg.ApiService
 import io.heckel.ntfy.msg.NotificationDispatcher
@@ -182,7 +183,7 @@ class SubscriberService : Service() {
                 }
                 if (!connections.containsKey(baseUrl)) {
                     val serviceActive = { -> isServiceStarted }
-                    val connection = if (true) {
+                    val connection = if (repository.getConnectionProtocol() == Repository.CONNECTION_PROTOCOL_WS) {
                         val alarmManager = getSystemService(ALARM_SERVICE) as AlarmManager
                         WsConnection(repository, baseUrl, since, subscriptions, ::onStateChanged, ::onNotificationReceived, alarmManager)
                     } else {

app/src/main/java/io/heckel/ntfy/service/WsConnection.kt

@@ -2,12 +2,15 @@ package io.heckel.ntfy.service
 
 import android.app.AlarmManager
 import android.os.Build
+import android.os.Handler
+import android.os.Looper
 import android.util.Log
-import com.google.gson.Gson
+import io.heckel.ntfy.data.ConnectionState
-import io.heckel.ntfy.data.*
+import io.heckel.ntfy.data.Notification
-import io.heckel.ntfy.msg.ApiService
+import io.heckel.ntfy.data.Repository
-import io.heckel.ntfy.util.joinTags
+import io.heckel.ntfy.data.Subscription
-import io.heckel.ntfy.util.toPriority
+import io.heckel.ntfy.msg.NotificationParser
+import io.heckel.ntfy.util.topicUrl
 import io.heckel.ntfy.util.topicUrlWs
 import okhttp3.*
 import java.util.*
@@ -24,34 +27,20 @@ class WsConnection(
     private val notificationListener: (Subscription, Notification) -> Unit,
     private val alarmManager: AlarmManager
 ) : Connection {
-    private val client: OkHttpClient
+    private val parser = NotificationParser()
-    //private val reconnectHandler = Handler()
+    private val client = OkHttpClient.Builder()
-    //private val reconnectCallback = Runnable { start() }
+        .readTimeout(0, TimeUnit.MILLISECONDS)
+        .pingInterval(1, TimeUnit.MINUTES)
+        .connectTimeout(10, TimeUnit.SECONDS)
+        .build()
     private var errorCount = 0
     private var webSocket: WebSocket? = null
     private var state: State? = null
-    private val gson = Gson()
 
+    private var since: Long = sinceTime
     private val subscriptionIds = topicsToSubscriptionIds.values
     private val topicsStr = topicsToSubscriptionIds.keys.joinToString(separator = ",")
-    private val sinceVal = if (sinceTime == 0L) "all" else sinceTime.toString()
+    private val url = topicUrl(baseUrl, topicsStr)
-    private val wsurl = topicUrlWs(baseUrl, topicsStr, sinceVal)
-
-    init {
-        val builder = OkHttpClient.Builder()
-            .readTimeout(0, TimeUnit.MILLISECONDS)
-            //.pingInterval(1, TimeUnit.MINUTES)
-            .pingInterval(30, TimeUnit.SECONDS)
-            .connectTimeout(10, TimeUnit.SECONDS)
-        client = builder.build()
-    }
-
-    private fun request(): Request {
-        return Request.Builder()
-            .url(wsurl)
-            .get()
-            .build()
-    }
 
     @Synchronized
     override fun start() {
@@ -61,22 +50,27 @@ class WsConnection(
         cancel()
         state = State.Connecting
         val nextId = ID.incrementAndGet()
-        Log.d(TAG, "WebSocket($nextId): starting...")
+        val sinceVal = if (since == 0L) "all" else since.toString()
-        webSocket = client.newWebSocket(request(), Listener(nextId))
+        val urlWithSince = topicUrlWs(baseUrl, topicsStr, sinceVal)
+        val request = Request.Builder().url(urlWithSince).get().build()
+        Log.d(TAG, "[$url] WebSocket($nextId): opening $urlWithSince ...")
+        webSocket = client.newWebSocket(request, Listener(nextId))
     }
 
     @Synchronized
     override fun cancel() {
-        if (webSocket != null) {
+        if (webSocket == null) {
-            Log.d(TAG, "WebSocket(" + ID.get() + "): closing existing connection.")
+            return
+        }
+        Log.d(TAG, "[$url] WebSocket(${ID.get()}): closing existing connection")
         state = State.Disconnected
         webSocket!!.close(1000, "")
         webSocket = null
     }
-    }
 
+    @Synchronized
     override fun since(): Long {
-        return 0L
+        return since
     }
 
     override fun matches(otherSubscriptionIds: Collection<Long>): Boolean {
@@ -84,39 +78,29 @@ class WsConnection(
     }
 
     @Synchronized
-    fun scheduleReconnect(seconds: Long) {
+    fun scheduleReconnect(seconds: Int) {
         if (state == State.Connecting || state == State.Connected) {
             return
         }
         state = State.Scheduled
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
-            Log.d(TAG,
+            Log.d(TAG,"[$url] WebSocket: Scheduling a restart in $seconds seconds (via alarm manager)")
-                "WebSocket: scheduling a restart in "
+            val reconnectTime = Calendar.getInstance()
-                        + seconds
+            reconnectTime.add(Calendar.SECOND, seconds)
-                        + " second(s) (via alarm manager)"
+            alarmManager.setExact(AlarmManager.RTC_WAKEUP, reconnectTime.timeInMillis, RECONNECT_TAG, { start() }, null)
-            )
-            val future = Calendar.getInstance()
-            future.add(Calendar.SECOND, seconds.toInt())
-            alarmManager.setExact(
-                AlarmManager.RTC_WAKEUP,
-                future.timeInMillis,
-                "reconnect-tag", { start() },
-                null
-            )
         } else {
-            Log.d(TAG, "WebSocket: scheduling a restart in $seconds second(s)")
+            Log.d(TAG, "[$url] WebSocket: Scheduling a restart in $seconds seconds (via handler)")
-            //reconnectHandler.removeCallbacks(reconnectCallback)
+            val handler = Handler(Looper.getMainLooper())
-            //reconnectHandler.postDelayed(reconnectCallback, TimeUnit.SECONDS.toMillis(seconds))
+            handler.postDelayed({ start() }, TimeUnit.SECONDS.toMillis(seconds.toLong()))
         }
     }
 
     private inner class Listener(private val id: Long) : WebSocketListener() {
         override fun onOpen(webSocket: WebSocket, response: Response) {
             syncExec {
+                Log.d(TAG, "[$url] WebSocket($id): opened")
                 state = State.Connected
-                Log.d(TAG, "WebSocket(" + id + "): opened")
                 if (errorCount > 0) {
-                    Log.d(TAG, "reconnected")
                     errorCount = 0
                 }
                 stateChangeListener(subscriptionIds, ConnectionState.CONNECTED)
@@ -125,65 +109,36 @@ class WsConnection(
 
         override fun onMessage(webSocket: WebSocket, text: String) {
             syncExec {
-                Log.d(TAG, "WebSocket(" + id + "): received message " + text)
+                Log.d(TAG, "[$url] WebSocket($id): received message: $text")
-                val message = gson.fromJson(text, ApiService.Message::class.java)
+                val notificationWithTopic = parser.parseWithTopic(text, subscriptionId = 0, notificationId = Random.nextInt())
-                if (message.event == ApiService.EVENT_MESSAGE) {
+                if (notificationWithTopic == null) {
-                    val topic = message.topic
+                    return@syncExec
-                    val attachment = if (message.attachment?.url != null) {
+                }
-                        Attachment(
+                val topic = notificationWithTopic.topic
-                            name = message.attachment.name,
+                val notification = notificationWithTopic.notification
-                            type = message.attachment.type,
-                            size = message.attachment.size,
-                            expires = message.attachment.expires,
-                            url = message.attachment.url,
-                        )
-                    } else null
-                    val notification = Notification(
-                        id = message.id,
-                        subscriptionId = 0, // TO BE SET downstream
-                        timestamp = message.time,
-                        title = message.title ?: "",
-                        message = message.message,
-                        priority = toPriority(message.priority),
-                        tags = joinTags(message.tags),
-                        click = message.click ?: "",
-                        attachment = attachment,
-                        notificationId = Random.nextInt(),
-                        deleted = false
-                    )
                 val subscriptionId = topicsToSubscriptionIds[topic] ?: return@syncExec
                 val subscription = repository.getSubscription(subscriptionId) ?: return@syncExec
                 val notificationWithSubscriptionId = notification.copy(subscriptionId = subscription.id)
                 notificationListener(subscription, notificationWithSubscriptionId)
-                }
+                since = notification.timestamp
             }
         }
 
         override fun onClosed(webSocket: WebSocket, code: Int, reason: String) {
             syncExec {
-                if (state == State.Connected) {
+                Log.w(TAG, "[$url] WebSocket($id): closed")
-                    Log.w(TAG, "WebSocket(" + id + "): closed")
-                }
                 state = State.Disconnected
             }
         }
 
         override fun onFailure(webSocket: WebSocket, t: Throwable, response: Response?) {
-            val code = if (response != null) "StatusCode: " + response.code else ""
+            Log.e(TAG, "[$url] WebSocket($id): failure ${response?.code}: ${response?.message}", t)
-            val message = response?.message ?: ""
-            Log.e(TAG, "WebSocket($id): failure $code Message: $message", t)
             syncExec {
                 stateChangeListener(subscriptionIds, ConnectionState.CONNECTING)
                 state = State.Disconnected
-                if ((response != null) && (response.code >= 400) && (response.code <= 499)) {
-                    Log.d(TAG, "bad request")
-                    cancel()
-                    return@syncExec
-                }
                 errorCount++
-                val minutes: Int = Math.min(errorCount * 2 - 1, 20)
+                val retrySeconds = RETRY_SECONDS.getOrNull(errorCount) ?: RETRY_SECONDS.last()
-                //scheduleReconnect(TimeUnit.MINUTES.toSeconds(minutes.toLong()))
+                scheduleReconnect(retrySeconds)
-                scheduleReconnect(30)
             }
         }
 
@@ -202,6 +157,8 @@ class WsConnection(
 
     companion object {
         private const val TAG = "NtfyWsConnection"
+        private const val RECONNECT_TAG = "WsReconnect"
+        private val RETRY_SECONDS = listOf(5, 10, 15, 20, 30, 45, 60, 120)
         private val ID = AtomicLong(0)
     }
 }

app/src/main/java/io/heckel/ntfy/ui/SettingsActivity.kt

@@ -153,6 +153,27 @@ class SettingsActivity : AppCompatActivity() {
                 }
             }
 
+            // Connection protocol
+            val connectionProtocolPrefId = context?.getString(R.string.settings_advanced_connection_protocol_key) ?: return
+            val connectionProtocol: ListPreference? = findPreference(connectionProtocolPrefId)
+            connectionProtocol?.value = repository.getConnectionProtocol()
+            connectionProtocol?.preferenceDataStore = object : PreferenceDataStore() {
+                override fun putString(key: String?, value: String?) {
+                    val proto = value ?: repository.getConnectionProtocol()
+                    repository.setConnectionProtocol(proto)
+                    restartService()
+                }
+                override fun getString(key: String?, defValue: String?): String {
+                    return repository.getConnectionProtocol()
+                }
+            }
+            connectionProtocol?.summaryProvider = Preference.SummaryProvider<ListPreference> { pref ->
+                when (pref.value) {
+                    Repository.CONNECTION_PROTOCOL_WS -> getString(R.string.settings_advanced_connection_protocol_summary_ws)
+                    else -> getString(R.string.settings_advanced_connection_protocol_summary_jsonhttp)
+                }
+            }
+
             // Permanent wakelock enabled
             val wakelockEnabledPrefId = context?.getString(R.string.settings_advanced_wakelock_key) ?: return
             val wakelockEnabled: SwitchPreference? = findPreference(wakelockEnabledPrefId)
@@ -160,11 +181,7 @@ class SettingsActivity : AppCompatActivity() {
             wakelockEnabled?.preferenceDataStore = object : PreferenceDataStore() {
                 override fun putBoolean(key: String?, value: Boolean) {
                     repository.setWakelockEnabled(value)
-                    val context = this@SettingsFragment.context
+                    restartService()
-                    Intent(context, SubscriberService::class.java).also { intent ->
-                        // Service will autorestart
-                        context?.stopService(intent)
-                    }
                 }
                 override fun getBoolean(key: String?, defValue: Boolean): Boolean {
                     return repository.getWakelockEnabled()
@@ -265,6 +282,13 @@ class SettingsActivity : AppCompatActivity() {
             autoDownload?.value = autoDownloadSelectionCopy.toString()
             repository.setAutoDownloadMaxSize(autoDownloadSelectionCopy)
         }
+
+        private fun restartService() {
+            val context = this@SettingsFragment.context
+            Intent(context, SubscriberService::class.java).also { intent ->
+                context?.stopService(intent) // Service will auto-restart
+            }
+        }
     }
 
     override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<String>, grantResults: IntArray) {

app/src/main/res/values/strings.xml

@@ -226,6 +226,12 @@
     <string name="settings_unified_push_base_url_title">Server URL</string>
     <string name="settings_unified_push_base_url_default_summary">%1$s (default)</string>
     <string name="settings_advanced_header">Advanced</string>
+    <string name="settings_advanced_connection_protocol_key">ConnectionProtocol</string>
+    <string name="settings_advanced_connection_protocol_title">Connection protocol</string>
+    <string name="settings_advanced_connection_protocol_summary_jsonhttp">Use a JSON stream over HTTP to connect to the server. This is the tried and true method, though it may consume more battery.</string>
+    <string name="settings_advanced_connection_protocol_summary_ws">Use WebSockets to connect to the server. This option is experimental. Let us know if it consumes less battery or is unstable.</string>
+    <string name="settings_advanced_connection_protocol_entry_jsonhttp">JSON stream over HTTP</string>
+    <string name="settings_advanced_connection_protocol_entry_ws">WebSockets (experimental)</string>
     <string name="settings_advanced_wakelock_key">WakelockEnabled</string>
     <string name="settings_advanced_wakelock_title">Permanent wakelock</string>
     <string name="settings_advanced_wakelock_summary_enabled">Prevents app from sleeping to ensure timely notification delivery. This consumes a lot of battery, but some devices require this.</string>

app/src/main/res/values/values.xml

@@ -34,4 +34,12 @@
         <item>10485760</item>
         <item>52428800</item>
     </string-array>
+    <string-array name="settings_advanced_connection_protocol_entries">
+        <item>@string/settings_advanced_connection_protocol_entry_jsonhttp</item>
+        <item>@string/settings_advanced_connection_protocol_entry_ws</item>
+    </string-array>
+    <string-array name="settings_advanced_connection_protocol_values">
+        <item>jsonhttp</item>
+        <item>ws</item>
+    </string-array>
 </resources>

app/src/main/res/xml/main_preferences.xml

@@ -34,6 +34,12 @@
                 app:dependency="@string/settings_unified_push_enabled_key"/>
     </PreferenceCategory>
     <PreferenceCategory app:title="@string/settings_advanced_header">
+        <ListPreference
+                app:key="@string/settings_advanced_connection_protocol_key"
+                app:title="@string/settings_advanced_connection_protocol_title"
+                app:entries="@array/settings_advanced_connection_protocol_entries"
+                app:entryValues="@array/settings_advanced_connection_protocol_values"
+                app:defaultValue="jsonhttp"/>
         <SwitchPreference
             app:key="@string/settings_advanced_wakelock_key"
             app:title="@string/settings_advanced_wakelock_title"