feat: Add host auto-discovery and xemu setup improvements

README.md

@@ -184,7 +184,9 @@ The repository now includes `.run/Run xemu.run.xml`, which launches `scripts\run
 
 If you create a local CLion run configuration that sets the working directory to a build output such as `$CMakeCurrentBuildDir$/xbox`, the Windows wrapper also treats that caller working directory as the xemu target path when no explicit launcher arguments or `MOONLIGHT_XEMU_*` overrides are provided.
 
-The setup script downloads xemu and the emulator support files into `.local/xemu`, then refreshes launcher manifests used by `scripts/run-xemu.sh`. The launcher accepts `MOONLIGHT_XEMU_BUILD_DIR`, `MOONLIGHT_XEMU_ISO_PATH`, `--build-dir <cmake-build-dir>`, `--iso <iso-path>`, or a single positional path that can point at either a build directory or an ISO file. If you do not pass a path, it falls back across available `cmake-build-*` outputs and prefers the newest built ISO.
+The setup script downloads xemu and the emulator support files into `.local/xemu`, then refreshes launcher manifests used by `scripts/run-xemu.sh`. Existing files under `.local/xemu` are preserved by default so a local xemu install or support bundle is not overwritten unless you pass `--force`. The launcher accepts `MOONLIGHT_XEMU_BUILD_DIR`, `MOONLIGHT_XEMU_ISO_PATH`, `--build-dir <cmake-build-dir>`, `--iso <iso-path>`, or a single positional path that can point at either a build directory or an ISO file. If you do not pass a path, it falls back across available `cmake-build-*` outputs and prefers the newest built ISO.
+
+When xemu runs with its default user-mode network, multicast mDNS traffic is not forwarded reliably, so automatic host discovery may not find your PC. For reliable discovery, launch xemu with `--network tap --tap-ifname <adapter>` or add the host manually from the Xbox UI.
 
 If you only want the emulator without the ROM/HDD support bundle, run:
 
@@ -241,6 +243,7 @@ scripts\setup-xemu.cmd --skip-support-files
 - Misc.
   - [x] Save config and pairing states
   - [x] Host pairing
+  - [x] Auto host discovery
   - [ ] Possibly, GPU overclocking, see https://github.com/GXTX/XboxOverclock
 
 <details style="display: none;">

cmake/moonlight-dependencies.cmake

@@ -55,6 +55,11 @@ macro(MOONLIGHT_PREPARE_COMMON_DEPENDENCIES)
         set(MOONLIGHT_NXDK_NET_INCLUDE_DIR "${NXDK_DIR}/lib/net")
         set(MOONLIGHT_NXDK_LIBC_EXTENSIONS_DIR "${NXDK_DIR}/lib/xboxrt/libc_extensions")
         set(MOONLIGHT_NXDK_LWIP_POSIX_COMPAT_DIR "${NXDK_DIR}/lib/net/lwip/src/include/compat/posix")
+        set(MOONLIGHT_NXDK_LWIP_MDNS_SOURCES
+                "${NXDK_DIR}/lib/net/lwip/src/apps/mdns/mdns.c"
+                "${NXDK_DIR}/lib/net/lwip/src/apps/mdns/mdns_domain.c"
+                "${NXDK_DIR}/lib/net/lwip/src/apps/mdns/mdns_out.c"
+        )
 
         if(TARGET enet)
             target_link_libraries(enet PUBLIC NXDK::NXDK NXDK::Net)

cmake/xbox-build.cmake

@@ -56,7 +56,9 @@ add_executable(${CMAKE_PROJECT_NAME}
 )
 target_sources(${CMAKE_PROJECT_NAME}
         PRIVATE
-        "${CMAKE_SOURCE_DIR}/src/_nxdk_compat/stat_compat.cpp")
+        "${CMAKE_SOURCE_DIR}/src/_nxdk_compat/stat_compat.cpp"
+        ${MOONLIGHT_NXDK_LWIP_MDNS_SOURCES}
+)
 target_include_directories(${CMAKE_PROJECT_NAME}
         SYSTEM PRIVATE
         "${CMAKE_CURRENT_SOURCE_DIR}"

scripts/setup-xemu.sh

@@ -7,6 +7,7 @@ usage() {
 Usage: setup-xemu.sh [--force] [--skip-support-files]
 
 Downloads a portable xemu build into .local/xemu and refreshes launcher manifests.
+Existing .local/xemu files are preserved unless --force is passed.
 EOF
     return 0
 }
@@ -68,6 +69,33 @@ extract_archive() {
     return 1
 }
 
+copy_tree_preserving_existing() {
+    local source_root="$1"
+    local destination_root="$2"
+    local source_path relative_path destination_path
+
+    mkdir -p "$destination_root"
+
+    while IFS= read -r -d '' source_path; do
+        relative_path="${source_path#"$source_root"/}"
+        destination_path="$destination_root/$relative_path"
+
+        if [[ -d "$source_path" ]]; then
+            mkdir -p "$destination_path"
+            continue
+        fi
+
+        if [[ -e "$destination_path" ]]; then
+            continue
+        fi
+
+        mkdir -p "$(dirname "$destination_path")"
+        cp -p "$source_path" "$destination_path"
+    done < <(find "$source_root" -mindepth 1 -print0)
+
+    return 0
+}
+
 latest_xemu_tag() {
     curl -fsSL -A 'Moonlight-XboxOG setup-xemu' \
         'https://api.github.com/repos/xemu-project/xemu/releases/latest' |
@@ -147,6 +175,22 @@ find_first_file() {
     return 1
 }
 
+find_existing_xemu_executable() {
+    local root="$1"
+
+    find_first_file "$root" 'xemu.exe' 'xemu' 'xemu.AppImage'
+    return $?
+}
+
+support_assets_ready() {
+    local root="$1"
+
+    [[ -n "$(find_first_file "$root" 'mcpx*.bin' 2>/dev/null || true)" ]] || return 1
+    [[ -n "$(find_first_file "$root" 'Complex*.bin' '*4627*.bin' 2>/dev/null || true)" ]] || return 1
+    [[ -n "$(find_first_file "$root" 'xbox_hdd.qcow2' '*.qcow2' 2>/dev/null || true)" ]] || return 1
+    return 0
+}
+
 write_shell_manifest() {
     local manifest_path="$1"
     shift
@@ -179,6 +223,8 @@ write_cmd_manifest() {
 
 force_download=0
 skip_support_files=0
+reused_existing_xemu=0
+reused_existing_support=0
 
 while [[ $# -gt 0 ]]; do
     case "$1" in
@@ -214,56 +260,79 @@ manifest_cmd="$xemu_root/paths.cmd"
 
 mkdir -p "$downloads_dir" "$app_dir" "$support_dir" "$temp_dir" "$portable_root"
 
-mapfile -t platform_info < <(detect_platform)
-os_name="${platform_info[0]}"
-arch_name="${platform_info[1]}"
-tag="$(latest_xemu_tag)"
-if [[ -z "$tag" ]]; then
-    echo 'Could not determine the latest xemu release tag.' >&2
-    exit 1
-fi
-
-asset_name="$(select_xemu_asset "$os_name" "$arch_name" "$tag")"
-asset_url="https://github.com/xemu-project/xemu/releases/latest/download/${asset_name}"
-asset_path="$downloads_dir/$asset_name"
-
-download_file "$asset_url" "$asset_path" "$force_download"
-
-rm -rf "$app_dir"
-mkdir -p "$app_dir"
+xemu_exe="$(find_existing_xemu_executable "$app_dir" || true)"
+if [[ -n "$xemu_exe" && "$force_download" -eq 0 ]]; then
+    reused_existing_xemu=1
+else
+    mapfile -t platform_info < <(detect_platform)
+    os_name="${platform_info[0]}"
+    arch_name="${platform_info[1]}"
+    tag="$(latest_xemu_tag)"
+    if [[ -z "$tag" ]]; then
+        echo 'Could not determine the latest xemu release tag.' >&2
+        exit 1
+    fi
 
-case "$asset_name" in
-    *.zip)
-        extract_archive "$asset_path" "$temp_dir/xemu-extract"
-        xemu_exe="$(find_first_file "$temp_dir/xemu-extract" 'xemu.exe' 'xemu')"
-        if [[ -z "$xemu_exe" ]]; then
-            echo 'Could not find xemu executable in the downloaded archive.' >&2
+    asset_name="$(select_xemu_asset "$os_name" "$arch_name" "$tag")"
+    asset_url="https://github.com/xemu-project/xemu/releases/latest/download/${asset_name}"
+    asset_path="$downloads_dir/$asset_name"
+
+    download_file "$asset_url" "$asset_path" "$force_download"
+
+    case "$asset_name" in
+        *.zip)
+            extract_archive "$asset_path" "$temp_dir/xemu-extract"
+            if [[ -z "$(find_existing_xemu_executable "$temp_dir/xemu-extract" || true)" ]]; then
+                echo 'Could not find xemu executable in the downloaded archive.' >&2
+                exit 1
+            fi
+
+            if [[ "$force_download" -eq 1 ]]; then
+                rm -rf "$app_dir"
+                mkdir -p "$app_dir"
+                cp -R "$temp_dir/xemu-extract"/. "$app_dir"/
+            else
+                copy_tree_preserving_existing "$temp_dir/xemu-extract" "$app_dir"
+            fi
+            xemu_exe="$(find_existing_xemu_executable "$app_dir" || true)"
+            ;;
+        *.AppImage)
+            if [[ "$force_download" -eq 1 || ! -f "$app_dir/xemu.AppImage" ]]; then
+                cp "$asset_path" "$app_dir/xemu.AppImage"
+            fi
+            chmod +x "$app_dir/xemu.AppImage"
+            xemu_exe="$app_dir/xemu.AppImage"
+            ;;
+        *)
+            echo "Unsupported xemu asset type: $asset_name" >&2
             exit 1
-        fi
-        cp -R "$temp_dir/xemu-extract"/. "$app_dir"/
-        xemu_exe="$(find_first_file "$app_dir" 'xemu.exe' 'xemu')"
-        ;;
-    *.AppImage)
-        cp "$asset_path" "$app_dir/xemu.AppImage"
-        chmod +x "$app_dir/xemu.AppImage"
-        xemu_exe="$app_dir/xemu.AppImage"
-        ;;
-    *)
-        echo "Unsupported xemu asset type: $asset_name" >&2
+            ;;
+    esac
+
+    if [[ -z "$xemu_exe" ]]; then
+        echo 'Could not locate the xemu executable after installation.' >&2
         exit 1
-        ;;
- esac
+    fi
+fi
 
 support_zip="$downloads_dir/Xbox-Emulator-Files.zip"
 if [[ "$skip_support_files" -eq 0 ]]; then
-    download_file \
-        'https://github.com/K3V1991/Xbox-Emulator-Files/releases/download/v1/Xbox-Emulator-Files.zip' \
-        "$support_zip" \
-        "$force_download"
-    rm -rf "$support_dir"
-    mkdir -p "$support_dir"
-    extract_archive "$support_zip" "$temp_dir/support-extract"
-    cp -R "$temp_dir/support-extract"/. "$support_dir"/
+    if [[ "$force_download" -eq 0 ]] && support_assets_ready "$support_dir"; then
+        reused_existing_support=1
+    else
+        download_file \
+            'https://github.com/K3V1991/Xbox-Emulator-Files/releases/download/v1/Xbox-Emulator-Files.zip' \
+            "$support_zip" \
+            "$force_download"
+        extract_archive "$support_zip" "$temp_dir/support-extract"
+        if [[ "$force_download" -eq 1 ]]; then
+            rm -rf "$support_dir"
+            mkdir -p "$support_dir"
+            cp -R "$temp_dir/support-extract"/. "$support_dir"/
+        else
+            copy_tree_preserving_existing "$temp_dir/support-extract" "$support_dir"
+        fi
+    fi
 fi
 
 bootrom_path=''
@@ -352,6 +421,12 @@ fi
 chmod +x "$manifest_sh"
 
 printf 'Portable xemu files are ready in %s\n' "$xemu_root"
+if [[ "$reused_existing_xemu" -eq 1 ]]; then
+    echo 'Reused the existing xemu application files in .local/xemu/app.'
+fi
+if [[ "$reused_existing_support" -eq 1 ]]; then
+    echo 'Reused the existing xemu support files in .local/xemu/support.'
+fi
 if [[ "$skip_support_files" -eq 1 ]]; then
     echo 'Support files were skipped. Run setup-xemu.sh again without --skip-support-files to fetch them.'
 elif [[ -z "$bootrom_path" || -z "$flashrom_path" || -z "$hdd_path" ]]; then

src/app/client_state.cpp

@@ -944,7 +944,7 @@ namespace {
    * @param update Update structure that receives the pairing request details.
    */
   void request_host_pairing(app::ClientState &state, const app::HostRecord &host, app::AppUpdate *update) {
-    if (!enter_pair_host_screen(state, host.address, host.port)) {
+    if (const uint16_t pairingPort = host.resolvedHttpPort == 0U ? host.port : host.resolvedHttpPort; !enter_pair_host_screen(state, host.address, pairingPort)) {
       return;
     }
 
@@ -1323,6 +1323,51 @@ namespace app {
     }
   }
 
+  bool merge_discovered_host(ClientState &state, std::string displayName, const std::string &address, uint16_t port) {
+    const std::string normalizedAddress = normalize_ipv4_address(address);
+    if (normalizedAddress.empty()) {
+      return false;
+    }
+
+    const uint16_t effectivePort = effective_host_port(port);
+    const uint16_t storedPort = effectivePort == DEFAULT_HOST_PORT ? 0 : effectivePort;
+    if (HostRecord *host = find_host_by_endpoint(state.hosts.items, normalizedAddress, effectivePort); host != nullptr) {
+      bool persistedMetadataChanged = false;
+      if (const std::string defaultDisplayName = build_default_host_display_name(host->address); !displayName.empty() && (host->displayName.empty() || host->displayName == defaultDisplayName)) {
+        persistedMetadataChanged = host->displayName != displayName;
+        host->displayName = std::move(displayName);
+      }
+      host->reachability = HostReachability::online;
+      if (host->manualAddress.empty()) {
+        host->manualAddress = normalizedAddress;
+      }
+      if (host->resolvedHttpPort == 0U || host->resolvedHttpPort == DEFAULT_HOST_PORT) {
+        host->resolvedHttpPort = effectivePort;
+      }
+      state.hosts.dirty = state.hosts.dirty || persistedMetadataChanged;
+      return persistedMetadataChanged;
+    }
+
+    HostRecord discoveredHost = make_host_record(normalizedAddress, storedPort);
+    if (!displayName.empty()) {
+      discoveredHost.displayName = std::move(displayName);
+    }
+    discoveredHost.reachability = HostReachability::online;
+    discoveredHost.manualAddress = normalizedAddress;
+    discoveredHost.resolvedHttpPort = effectivePort;
+
+    const bool wasEmpty = state.hosts.items.empty();
+    state.hosts.items.push_back(std::move(discoveredHost));
+    state.hosts.loaded = true;
+    state.hosts.dirty = true;
+    if (wasEmpty && state.shell.activeScreen == ScreenId::hosts) {
+      state.hosts.focusArea = HostsFocusArea::grid;
+      state.hosts.selectedHostIndex = 0U;
+    }
+    clamp_selected_host_index(state);
+    return true;
+  }
+
   void replace_saved_files(ClientState &state, std::vector<startup::SavedFileEntry> savedFiles) {
     state.settings.savedFiles = std::move(savedFiles);
     state.settings.savedFilesDirty = false;

src/app/client_state.h

@@ -413,6 +413,23 @@ namespace app {
    */
   void replace_hosts(ClientState &state, std::vector<HostRecord> hosts, std::string statusMessage = {});
 
+  /**
+   * @brief Add or refresh one auto-discovered host in the current host list.
+   *
+   * Discovery results are normalized to the same saved-host conventions used by
+   * manual host entry. When a matching host already exists, transient runtime
+   * fields such as reachability are refreshed without overwriting a custom saved
+   * name. When no host matches, a new host record is appended and marked dirty so
+   * it can be persisted.
+   *
+   * @param state Mutable app state.
+   * @param displayName Discovered host name, or an empty string to use the default label.
+   * @param address Discovered IPv4 address.
+   * @param port Discovered host HTTP port.
+   * @return true when persisted host metadata changed or a new host was added.
+   */
+  bool merge_discovered_host(ClientState &state, std::string displayName, const std::string &address, uint16_t port);
+
   /**
    * @brief Replace the in-memory saved-file inventory shown on the settings page.
    *