diff --git a/src/plugin/ChildProcess.hpp b/src/plugin/ChildProcess.hpp
index d92988e..d85dba0 100644
--- a/src/plugin/ChildProcess.hpp
+++ b/src/plugin/ChildProcess.hpp
@@ -223,10 +223,10 @@ class ChildProcess
        #else
         if (pid <= 0)
             return false;
-        
+
         const pid_t ret = ::waitpid(pid, nullptr, WNOHANG);
 
-        if (ret == -1 && errno == ECHILD)
+        if (ret == pid || (ret == -1 && errno == ECHILD))
         {
             pid = 0;
             return false;
diff --git a/src/plugin/DesktopPlugin.cpp b/src/plugin/DesktopPlugin.cpp
index 0b12223..2d70cdf 100644
--- a/src/plugin/DesktopPlugin.cpp
+++ b/src/plugin/DesktopPlugin.cpp
@@ -19,6 +19,8 @@ class DesktopPlugin : public Plugin,
     ChildProcess jackd;
     ChildProcess mod_ui;
     SharedMemory shm;
+    bool startingJackd = false;
+    bool startingModUI = false;
     bool processing = false;
     bool firstTimeProcessing = true;
     float parameters[kParameterCount] = {};
@@ -42,9 +44,17 @@ class DesktopPlugin : public Plugin,
             return;
 
         // TODO check available ports
-        portBaseNum = 1;
+        int availablePortNum = 1;
 
-        envp = getEvironment(portBaseNum);
+        envp = getEvironment(availablePortNum);
+
+        if (envp == nullptr)
+        {
+            parameters[kParameterBasePortNumber] = -kErrorAppDirNotFound;
+            return;
+        }
+
+        portBaseNum = availablePortNum;
 
         if (shm.init() && run())
             startRunner(500);
@@ -92,6 +102,13 @@ class DesktopPlugin : public Plugin,
 
         if (! jackd.isRunning())
         {
+            if (startingJackd)
+            {
+                startingJackd = false;
+                parameters[kParameterBasePortNumber] = -kErrorJackdExecFailed;
+                return false;
+            }
+
             const String appDir(getAppDir());
             const String jackdStr(appDir + DISTRHO_OS_SEP_STR "jackd" APP_EXT);
             const String jacksessionStr(appDir + DISTRHO_OS_SEP_STR "jack" DISTRHO_OS_SEP_STR "jack-session.conf");
@@ -109,9 +126,16 @@ class DesktopPlugin : public Plugin,
                 nullptr
             };
 
-            return jackd.start(jackd_args, envp);
+            startingJackd = true;
+            if (jackd.start(jackd_args, envp))
+                return true;
+
+            parameters[kParameterBasePortNumber] = -kErrorJackdExecFailed;
+            return false;
         }
 
+        startingJackd = false;
+
         if (! processing)
         {
             if (shm.sync())
@@ -122,6 +146,13 @@ class DesktopPlugin : public Plugin,
 
         if (! mod_ui.isRunning())
         {
+            if (startingModUI)
+            {
+                startingModUI = false;
+                parameters[kParameterBasePortNumber] = -kErrorModUiExecFailed;
+                return false;
+            }
+
             const String appDir(getAppDir());
             const String moduiStr(appDir + DISTRHO_OS_SEP_STR "mod-ui" APP_EXT);
 
@@ -130,9 +161,16 @@ class DesktopPlugin : public Plugin,
                 nullptr
             };
 
-            return mod_ui.start(mod_ui_args, envp);
+            startingModUI = true;
+            if (mod_ui.start(mod_ui_args, envp))
+                return true;
+
+            parameters[kParameterBasePortNumber] = -kErrorModUiExecFailed;
+            return false;
         }
 
+        startingModUI = false;
+
         parameters[kParameterBasePortNumber] = portBaseNum;
         return true;
     }
@@ -218,7 +256,7 @@ class DesktopPlugin : public Plugin,
             parameter.hints = kParameterIsOutput | kParameterIsInteger;
             parameter.name = "base port number";
             parameter.symbol = "base_port_num";
-            parameter.ranges.min = 0.f;
+            parameter.ranges.min = -kErrorUndefined;
             parameter.ranges.max = 512.f;
             parameter.ranges.def = 0.f;
             break;
diff --git a/src/plugin/DesktopUI.cpp b/src/plugin/DesktopUI.cpp
index 740ea3e..84d2910 100644
--- a/src/plugin/DesktopUI.cpp
+++ b/src/plugin/DesktopUI.cpp
@@ -19,6 +19,8 @@ class DesktopUI : public UI,
     Button buttonOpenWebGui;
     Button buttonOpenUserFilesDir;
     String label;
+    String error;
+    String errorDetail;
     uint port = 0;
     void* webview = nullptr;
 
@@ -85,6 +87,41 @@ class DesktopUI : public UI,
     {
         if (index == kParameterBasePortNumber)
         {
+            if (d_isZero(value))
+                return;
+
+            if (value < 0.f)
+            {
+                switch (-d_roundToIntNegative(value))
+                {
+                case kErrorAppDirNotFound:
+                    error = "Error: MOD Desktop application directory not found";
+                    errorDetail = "Make sure to install the standalone and run it at least once";
+                    break;
+                case kErrorJackdExecFailed:
+                    error = "Error: Failed to start jackd";
+                    errorDetail = "";
+                    break;
+                case kErrorModUiExecFailed:
+                    error = "Error: Failed to start mod-ui";
+                    errorDetail = "";
+                    break;
+                case kErrorUndefined:
+                    error = "Error initializing MOD Desktop plugin";
+                    errorDetail = "";
+                    break;
+                }
+                repaint();
+                return;
+            }
+
+            if (error.isNotEmpty())
+            {
+                error.clear();
+                errorDetail.clear();
+                repaint();
+            }
+
             if (webview != nullptr)
             {
                 destroyWebView(webview);
@@ -119,9 +156,21 @@ class DesktopUI : public UI,
         const double scaleFactor = getScaleFactor();
 
         fillColor(255, 255, 255, 255);
-        fontSize(14 * scaleFactor);
+        fontSize(18 * scaleFactor);
         textAlign(ALIGN_CENTER | ALIGN_MIDDLE);
         text(getWidth() / 2, kVerticalOffset * scaleFactor / 2, label, nullptr);
+
+        if (error.isNotEmpty())
+        {
+            fontSize(36 * scaleFactor);
+            text(getWidth() / 2, getHeight() / 2 - 18 * scaleFactor, error, nullptr);
+
+            if (errorDetail.isNotEmpty())
+            {
+                fontSize(18 * scaleFactor);
+                text(getWidth() / 2, getHeight() / 2 + 18 * scaleFactor, errorDetail, nullptr);
+            }
+        }
     }
 
     void buttonClicked(SubWidget* const widget, int button) override
diff --git a/src/plugin/DistrhoPluginInfo.h b/src/plugin/DistrhoPluginInfo.h
index e261900..926c8be 100644
--- a/src/plugin/DistrhoPluginInfo.h
+++ b/src/plugin/DistrhoPluginInfo.h
@@ -27,6 +27,13 @@
 static const constexpr unsigned int kVerticalOffset = 30;
 static const constexpr unsigned int kPortNumOffset = 18190;
 
+enum Error {
+    kErrorAppDirNotFound = 1,
+    kErrorJackdExecFailed,
+    kErrorModUiExecFailed,
+    kErrorUndefined
+};
+
 enum Parameters {
     kParameterBasePortNumber,
     kParameterCount
diff --git a/src/plugin/Makefile b/src/plugin/Makefile
index 3fee3c7..cfca0d8 100644
--- a/src/plugin/Makefile
+++ b/src/plugin/Makefile
@@ -1,5 +1,9 @@
 #!/usr/bin/make -f
 
+export DISTRHO_NAMESPACE = DesktopDISTRHO
+export DGL_NAMESPACE = DesktopDGL
+export NVG_FONT_TEXTURE_FLAGS = NVG_IMAGE_NEAREST
+
 include ../DPF/Makefile.base.mk
 
 # ---------------------------------------------------------------------------------------------------------------------
@@ -50,7 +54,7 @@ $(TARGET_DIR)/MOD-Desktop-WebView: $(BUILD_DIR)/WebViewQt.cpp.o
 
 $(BUILD_DIR)/WebViewQt.cpp.o: BUILD_CXX_FLAGS += -std=gnu++14 $(shell $(PKG_CONFIG) --cflags Qt5WebEngineWidgets)
 
-include $(BUILD_DIR)/WebViewQt.cpp.d
+-include $(BUILD_DIR)/WebViewQt.cpp.d
 
 endif
 
diff --git a/src/plugin/WebViewQt.cpp b/src/plugin/WebViewQt.cpp
index 7630cfe..1269255 100644
--- a/src/plugin/WebViewQt.cpp
+++ b/src/plugin/WebViewQt.cpp
@@ -36,7 +36,7 @@ int main(int argc, char* argv[])
 
     printf("'%s' '%s'\n", argv[1], argv[2]);
 
-    if (argc == 3 && std::strcmp(argv[1], "-xembed") == 0)
+    if (argc == 4 && std::strcmp(argv[1], "-xembed") == 0)
     {
         const uintptr_t parentId = std::atoll(argv[2]);
         QWindow* const parentWindow = QWindow::fromWinId(parentId);
@@ -46,7 +46,7 @@ int main(int argc, char* argv[])
         webview.setFixedSize(DISTRHO_UI_DEFAULT_WIDTH, DISTRHO_UI_DEFAULT_HEIGHT - kVerticalOffset);
         webview.winId();
         webview.windowHandle()->setParent(parentWindow);
-        webview.setUrl(QUrl("http://127.0.0.1:18181/"));
+        webview.setUrl(QUrl(QString::fromLocal8Bit("http://127.0.0.1:") + QString::fromLocal8Bit(argv[3])));
         webview.show();
         return app.exec();
     }
diff --git a/src/plugin/WebViewX11.cpp b/src/plugin/WebViewX11.cpp
index a1e2f9d..7c16f28 100644
--- a/src/plugin/WebViewX11.cpp
+++ b/src/plugin/WebViewX11.cpp
@@ -24,7 +24,7 @@ struct WebViewIPC {
 
 // -----------------------------------------------------------------------------------------------------------
 
-void* addWebView(uintptr_t viewptr)
+void* addWebView(const uintptr_t parentWinId, const uint port)
 {
     char webviewTool[PATH_MAX] = {};
     {
@@ -60,10 +60,17 @@ void* addWebView(uintptr_t viewptr)
     WebViewIPC* const ipc = new WebViewIPC();
     ipc->display = display;
     ipc->childWindow = 0;
-    ipc->ourWindow = viewptr;
-
-    const String viewStr(viewptr);
-    const char* const args[] = { webviewTool, "-platform", "xcb", "-xembed", viewStr.buffer(), nullptr };
+    ipc->ourWindow = parentWinId;
+
+    const String embedIdStr(parentWinId);
+    const String portStr(port);
+    const char* const args[] = {
+        webviewTool,
+        "-platform", "xcb",
+        "-xembed", embedIdStr.buffer(),
+        portStr.buffer(),
+        nullptr
+    };
     ipc->p.start(args);
 
     return ipc;
diff --git a/src/plugin/utils.cpp b/src/plugin/utils.cpp
index 4f7a500..4d9c91c 100644
--- a/src/plugin/utils.cpp
+++ b/src/plugin/utils.cpp
@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: 2023 MOD Audio UG
+// SPDX-FileCopyrightText: 2023-2024 MOD Audio UG
 // SPDX-License-Identifier: AGPL-3.0-or-later
 
 #include "utils.hpp"
@@ -8,7 +8,7 @@
 #ifdef _WIN32
 #else
 #include <sys/stat.h>
-// #include <unistd.h>
+#include <unistd.h>
 #endif
 
 #if defined(__APPLE__)
@@ -37,84 +37,106 @@ constexpr uint8_t char2u8(const uint8_t c)
 
 // -----------------------------------------------------------------------------------------------------------
 
+// FIXME share with systray
 #ifdef _WIN32
-static const WCHAR* getAppDirW()
+static WCHAR char* getDataDirW()
 {
-    static WCHAR appDir[MAX_PATH] = {};
+    static WCHAR dataDir[MAX_PATH] = {};
 
-    if (appDir[0] == 0)
+    if (dataDir[0] == 0)
     {
-        // TODO
         SHGetSpecialFolderPathW(nullptr, dataDir, CSIDL_MYDOCUMENTS, false);
+        _wmkdir(dataDir);
+
         std::wcsncat(dataDir, L"\\MOD Desktop", MAX_PATH - 1);
+        _wmkdir(dataDir);
     }
 
-    return appDir;
+    return dataDir;
 }
-#endif
-
-const char* getAppDir()
+#else
+static const char* getDataDir()
 {
-   #ifdef DISTRHO_OS_MAC
-    return "/Applications/MOD Desktop.app/Contents/MacOS";
-   #else
-    static char appDir[PATH_MAX] = {};
+    static char dataDir[PATH_MAX] = {};
 
-    if (appDir[0] == 0)
+    if (dataDir[0] == 0)
     {
-       #if defined(_WIN32)
-       #else
-        char appDir[PATH_MAX] = {};
-
         // TODO
-        std::strncpy(appDir, filename, PATH_MAX - 1);
+        std::strncpy(dataDir, getenv("HOME"), PATH_MAX - 1);
+        mkdir(dataDir, 0777);
 
-        if (char* const c = std::strrchr(appDir, '/'))
-            *c = 0;
-       #endif
+        std::strncat(dataDir, "/Documents", PATH_MAX - 1);
+        mkdir(dataDir, 0777);
+
+        std::strncat(dataDir, "/MOD Desktop", PATH_MAX - 1);
+        mkdir(dataDir, 0777);
     }
 
-    return appDir;
-   #endif
+    return dataDir;
 }
+#endif
+
+// -----------------------------------------------------------------------------------------------------------
 
 #ifdef _WIN32
-WCHAR char* getDataDirW()
+static const WCHAR* getAppDirW()
 {
-    static WCHAR dataDir[MAX_PATH] = {};
+    static WCHAR appDir[MAX_PATH] = {};
 
-    if (dataDir[0] == 0)
+    if (appDir[0] == 0)
     {
+        // TODO
         SHGetSpecialFolderPathW(nullptr, dataDir, CSIDL_MYDOCUMENTS, false);
-        _wmkdir(dataDir);
-
         std::wcsncat(dataDir, L"\\MOD Desktop", MAX_PATH - 1);
-        _wmkdir(dataDir);
     }
 
-    return dataDir;
+    return appDir;
 }
-#else
-const char* getDataDir()
+#endif
+
+const char* getAppDir()
 {
-    static char dataDir[PATH_MAX] = {};
+   #ifdef DISTRHO_OS_MAC
+    return "/Applications/MOD Desktop.app/Contents/MacOS";
+   #else
+    static char appDir[PATH_MAX] = {};
 
-    if (dataDir[0] == 0)
+    if (appDir[0] == 0)
     {
+       #if defined(_WIN32)
+        const WCHAR* const appDirW = getAppDirW();
+
         // TODO
-        std::strncpy(dataDir, getenv("HOME"), PATH_MAX - 1);
-        mkdir(dataDir, 0777);
+       #else
+        std::strncpy(appDir, getDataDir(), PATH_MAX - 1);
+        std::strncat(appDir, "/.last-known-location", PATH_MAX - 1);
 
-        std::strncat(dataDir, "/Documents", PATH_MAX - 1);
-        mkdir(dataDir, 0777);
+        if (FILE* const f = std::fopen(appDir, "r"))
+        {
+            std::memset(appDir, 0, PATH_MAX - 1);
 
-        std::strncat(dataDir, "/MOD Desktop", PATH_MAX - 1);
-        mkdir(dataDir, 0777);
+            if (std::fread(appDir, PATH_MAX - 1, 1, f) != 0)
+                appDir[0] = 0;
+
+            else if (access(appDir, F_OK) != 0)
+                appDir[0] = 0;
+
+            std::fclose(f);
+        }
+        else
+        {
+            appDir[0] = 0;
+            return nullptr;
+        }
+
+        if (appDir[0] == 0)
+            return nullptr;
+       #endif
     }
 
-    return dataDir;
+    return appDir;
+   #endif
 }
-#endif
 
 // -----------------------------------------------------------------------------------------------------------
 
@@ -162,6 +184,17 @@ static void set_envp_value(char** envp, const char* const key, const char* const
 // NOTE this needs to match initEvironment from systray side
 char* const* getEvironment(const uint portBaseNum)
 {
+    // get directory of the mod-desktop application
+   #ifdef _WIN32
+    const WCHAR* const appDir = getAppDirW();
+   #else
+    const char* const appDir = getAppDir();
+   #endif
+
+    // can be null, in case of not found
+    if (appDir == nullptr)
+        return nullptr;
+
    #ifdef DISTRHO_OS_MAC
     const char* const* const* const environptr = _NSGetEnviron();
     DISTRHO_SAFE_ASSERT_RETURN(environptr != nullptr, nullptr);
@@ -197,13 +230,6 @@ char* const* getEvironment(const uint portBaseNum)
     set_envp_value(envp, "PYTHONUNBUFFERED=1");
    #endif
 
-    // get directory of the mod-desktop application
-   #ifdef _WIN32
-    const WCHAR* const appDir = getAppDirW();
-   #else
-    const char* const appDir = getAppDir();
-   #endif
-
     // get and set directory to our documents and settings, under "user documents"; also make sure it exists
    #ifdef _WIN32
     const WCHAR* const dataDir = getDataDirW();
diff --git a/src/systray/utils.cpp b/src/systray/utils.cpp
index bd6114c..b94e022 100644
--- a/src/systray/utils.cpp
+++ b/src/systray/utils.cpp
@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: 2023 MOD Audio UG
+// SPDX-FileCopyrightText: 2023-2024 MOD Audio UG
 // SPDX-License-Identifier: AGPL-3.0-or-later
 
 #include "utils.hpp"
@@ -146,6 +146,21 @@ void initEvironment()
     const size_t dataDirLen = std::strlen(dataDir);
    #endif
 
+    // write our location to disk so the plugin version knows where to find us
+   #ifdef __linux__
+    if (access(dataDir, F_OK) == 0)
+    {
+        std::memcpy(path, dataDir, dataDirLen);
+        std::strncpy(path + dataDirLen, "/.last-known-location", PATH_MAX - dataDirLen - 1);
+
+        if (FILE* const f = std::fopen(path, "w"))
+        {
+            std::fwrite(appDir, appDirLen, 1, f);
+            std::fclose(f);
+        }
+    }
+   #endif
+
     // generate UID
     uint8_t key[16] = {};
    #if defined(__APPLE__)
@@ -178,9 +193,9 @@ void initEvironment()
    #elif defined(_WIN32)
     // TODO
    #else
-    if (FILE* const f = fopen("/etc/machine-id", "r"))
+    if (FILE* const f = std::fopen("/etc/machine-id", "r"))
     {
-        if (fread(path, PATH_MAX - 1, 1, f) == 0 && strlen(path) >= 33)
+        if (std::fread(path, PATH_MAX - 1, 1, f) == 0 && std::strlen(path) >= 33)
         {
             for (int i=0; i<16; ++i)
             {
@@ -188,7 +203,7 @@ void initEvironment()
                 key[i] |= char2u8(path[i*2+1]) << 0;
             }
         }
-        fclose(f);
+        std::fclose(f);
     }
    #endif