21 files changed, 939 insertions, 2 deletions

diff --git a/src/CommandLine.cxx b/src/CommandLine.cxx
index c5adc4153..19bc9d4bb 100644
--- a/src/CommandLine.cxx
+++ b/src/CommandLine.cxx
@@ -42,6 +42,11 @@
 #include "util/OptionDef.hxx"
 #include "util/OptionParser.hxx"
 
+#ifdef ENABLE_NEIGHBOR_PLUGINS
+#include "neighbor/Registry.hxx"
+#include "neighbor/NeighborPlugin.hxx"
+#endif
+
 #ifdef ENABLE_ENCODER
 #include "encoder/EncoderList.hxx"
 #include "encoder/EncoderPlugin.hxx"
@@ -104,6 +109,13 @@ static void version(void)
 	for (auto i = database_plugins; *i != nullptr; ++i)
 		printf(" %s", (*i)->name);
 
+#ifdef ENABLE_NEIGHBOR_PLUGINS
+	puts("\n\n"
+	     "Neighbor plugins:");
+	for (auto i = neighbor_plugins; *i != nullptr; ++i)
+		printf(" %s", (*i)->name);
+#endif
+
 	puts("\n\n"
 	     "Decoders plugins:");
 
@@ -148,7 +160,7 @@ static void version(void)
 #endif
 
 	puts("\n"
-	     "input/Input plugins:");
+	     "Input plugins:");
 	input_plugins_for_each(plugin)
 		printf(" %s", plugin->name);
 
diff --git a/src/Idle.cxx b/src/Idle.cxx
index bf08caa99..ed16bbecb 100644
--- a/src/Idle.cxx
+++ b/src/Idle.cxx
@@ -44,6 +44,7 @@ static const char *const idle_names[] = {
 	"update",
 	"subscription",
 	"message",
+	"neighbor",
 	nullptr
 };
 
diff --git a/src/Idle.hxx b/src/Idle.hxx
index a0fbad32c..7fc79d10a 100644
--- a/src/Idle.hxx
+++ b/src/Idle.hxx
@@ -59,6 +59,9 @@ static constexpr unsigned IDLE_SUBSCRIPTION = 0x200;
 /** a message on the subscribed channel was received */
 static constexpr unsigned IDLE_MESSAGE = 0x400;
 
+/** a neighbor was found or lost */
+static constexpr unsigned IDLE_NEIGHBOR = 0x800;
+
 /**
  * Adds idle flag (with bitwise "or") and queues notifications to all
  * clients.
diff --git a/src/Instance.cxx b/src/Instance.cxx
index 5b7c2de2d..16000afb3 100644
--- a/src/Instance.cxx
+++ b/src/Instance.cxx
@@ -54,3 +54,19 @@ Instance::OnDatabaseModified()
 {
 	DatabaseModified();
 }
+
+#ifdef ENABLE_NEIGHBOR_PLUGINS
+
+void
+Instance::FoundNeighbor(gcc_unused const NeighborInfo &info)
+{
+	idle_add(IDLE_NEIGHBOR);
+}
+
+void
+Instance::LostNeighbor(gcc_unused const NeighborInfo &info)
+{
+	idle_add(IDLE_NEIGHBOR);
+}
+
+#endif
diff --git a/src/Instance.hxx b/src/Instance.hxx
index ca7bb5197..a14719839 100644
--- a/src/Instance.hxx
+++ b/src/Instance.hxx
@@ -24,10 +24,24 @@
 #include "db/DatabaseListener.hxx"
 #include "Compiler.h"
 
+#ifdef ENABLE_NEIGHBOR_PLUGINS
+#include "neighbor/Listener.hxx"
+class NeighborGlue;
+#endif
+
 class ClientList;
 struct Partition;
 
-struct Instance final : public DatabaseListener {
+struct Instance final
+	: public DatabaseListener
+#ifdef ENABLE_NEIGHBOR_PLUGINS
+	, public NeighborListener
+#endif
+{
+#ifdef ENABLE_NEIGHBOR_PLUGINS
+	NeighborGlue *neighbors;
+#endif
+
 	ClientList *client_list;
 
 	Partition *partition;
@@ -53,6 +67,12 @@ struct Instance final : public DatabaseListener {
 
 private:
 	virtual void OnDatabaseModified();
+
+#ifdef ENABLE_NEIGHBOR_PLUGINS
+	/* virtual methods from class NeighborListener */
+	virtual void FoundNeighbor(const NeighborInfo &info) override;
+	virtual void LostNeighbor(const NeighborInfo &info) override;
+#endif
 };
 
 #endif
diff --git a/src/Main.cxx b/src/Main.cxx
index fc7efd036..f790ec574 100644
--- a/src/Main.cxx
+++ b/src/Main.cxx
@@ -67,6 +67,10 @@
 #include "config/ConfigOption.hxx"
 #include "Stats.hxx"
 
+#ifdef ENABLE_NEIGHBOR_PLUGINS
+#include "neighbor/Glue.hxx"
+#endif
+
 #ifdef ENABLE_INOTIFY
 #include "db/update/InotifyUpdate.hxx"
 #endif
@@ -394,6 +398,19 @@ int mpd_main(int argc, char *argv[])
 
 	instance = new Instance();
 
+#ifdef ENABLE_NEIGHBOR_PLUGINS
+	instance->neighbors = new NeighborGlue();
+	if (!instance->neighbors->Init(io_thread_get(), *instance, error)) {
+		LogError(error);
+		return EXIT_FAILURE;
+	}
+
+	if (instance->neighbors->IsEmpty()) {
+		delete instance->neighbors;
+		instance->neighbors = nullptr;
+	}
+#endif
+
 	const unsigned max_clients = config_get_positive(CONF_MAX_CONN, 10);
 	instance->client_list = new ClientList(max_clients);
 
@@ -460,6 +477,12 @@ int mpd_main(int argc, char *argv[])
 
 	io_thread_start();
 
+#ifdef ENABLE_NEIGHBOR_PLUGINS
+	if (instance->neighbors != nullptr &&
+	    !instance->neighbors->Open(error))
+		FatalError(error);
+#endif
+
 	ZeroconfInit(*main_loop);
 
 	player_create(instance->partition->pc);
@@ -523,6 +546,13 @@ int mpd_main(int argc, char *argv[])
 	listen_global_finish();
 	delete instance->client_list;
 
+#ifdef ENABLE_NEIGHBOR_PLUGINS
+	if (instance->neighbors != nullptr) {
+		instance->neighbors->Close();
+		delete instance->neighbors;
+	}
+#endif
+
 	const clock_t start = clock();
 	DatabaseGlobalDeinit();
 	FormatDebug(main_domain,
diff --git a/src/command/AllCommands.cxx b/src/command/AllCommands.cxx
index ce753b300..750fd1219 100644
--- a/src/command/AllCommands.cxx
+++ b/src/command/AllCommands.cxx
@@ -27,6 +27,7 @@
 #include "FileCommands.hxx"
 #include "OutputCommands.hxx"
 #include "MessageCommands.hxx"
+#include "NeighborCommands.hxx"
 #include "OtherCommands.hxx"
 #include "Permission.hxx"
 #include "tag/TagType.h"
@@ -99,6 +100,9 @@ static const struct command commands[] = {
 	{ "list", PERMISSION_READ, 1, -1, handle_list },
 	{ "listall", PERMISSION_READ, 0, 1, handle_listall },
 	{ "listallinfo", PERMISSION_READ, 0, 1, handle_listallinfo },
+#ifdef ENABLE_NEIGHBOR_PLUGINS
+	{ "listneighbors", PERMISSION_READ, 0, 0, handle_listneighbors },
+#endif
 	{ "listplaylist", PERMISSION_READ, 1, 1, handle_listplaylist },
 	{ "listplaylistinfo", PERMISSION_READ, 1, 1, handle_listplaylistinfo },
 	{ "listplaylists", PERMISSION_READ, 0, 0, handle_listplaylists },
@@ -179,6 +183,11 @@ command_available(gcc_unused const struct command *cmd)
 		return sticker_enabled();
 #endif
 
+#ifdef ENABLE_NEIGHBOR_PLUGINS
+	if (strcmp(cmd->cmd, "listneighbors") == 0)
+		return neighbor_commands_available();
+#endif
+
 	return true;
 }
 
diff --git a/src/command/NeighborCommands.cxx b/src/command/NeighborCommands.cxx
new file mode 100644
index 000000000..e68e8ef15
--- /dev/null
+++ b/src/command/NeighborCommands.cxx
@@ -0,0 +1,54 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "NeighborCommands.hxx"
+#include "client/Client.hxx"
+#include "Instance.hxx"
+#include "Main.hxx"
+#include "protocol/Result.hxx"
+#include "neighbor/Glue.hxx"
+#include "neighbor/Info.hxx"
+
+#include <set>
+#include <string>
+
+#include <assert.h>
+
+bool
+neighbor_commands_available()
+{
+	return instance->neighbors != nullptr;
+}
+
+CommandResult
+handle_listneighbors(Client &client,
+		     gcc_unused int argc, gcc_unused char *argv[])
+{
+	assert(instance->neighbors != nullptr);
+
+	const auto neighbors = instance->neighbors->GetList();
+	for (const auto &i : neighbors)
+		client_printf(client,
+			      "neighbor: %s\n"
+			      "name: %s\n",
+			      i.uri.c_str(),
+			      i.display_name.c_str());
+	return CommandResult::OK;
+}
diff --git a/src/command/NeighborCommands.hxx b/src/command/NeighborCommands.hxx
new file mode 100644
index 000000000..7bad946b4
--- /dev/null
+++ b/src/command/NeighborCommands.hxx
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_NEIGHBOR_COMMANDS_HXX
+#define MPD_NEIGHBOR_COMMANDS_HXX
+
+#include "CommandResult.hxx"
+#include "Compiler.h"
+
+class Client;
+
+gcc_pure
+bool
+neighbor_commands_available();
+
+CommandResult
+handle_listneighbors(Client &client, int argc, char *argv[]);
+
+#endif
diff --git a/src/config/ConfigOption.hxx b/src/config/ConfigOption.hxx
index 4ee108196..506c9e9dc 100644
--- a/src/config/ConfigOption.hxx
+++ b/src/config/ConfigOption.hxx
@@ -77,6 +77,7 @@ enum ConfigOption {
 	CONF_DESPOTIFY_HIGH_BITRATE,
 	CONF_AUDIO_FILTER,
 	CONF_DATABASE,
+	CONF_NEIGHBORS,
 	CONF_MAX
 };
 
diff --git a/src/config/ConfigTemplates.cxx b/src/config/ConfigTemplates.cxx
index e9cd68b5b..8eaa22bdd 100644
--- a/src/config/ConfigTemplates.cxx
+++ b/src/config/ConfigTemplates.cxx
@@ -77,6 +77,7 @@ const ConfigTemplate config_templates[] = {
 	{ "despotify_high_bitrate", false, false },
 	{ "filter", true, true },
 	{ "database", false, true },
+	{ "neighbors", true, true },
 };
 
 static constexpr unsigned n_config_templates =
diff --git a/src/neighbor/Explorer.hxx b/src/neighbor/Explorer.hxx
new file mode 100644
index 000000000..84a54840c
--- /dev/null
+++ b/src/neighbor/Explorer.hxx
@@ -0,0 +1,71 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_NEIGHBOR_EXPLORER_HXX
+#define MPD_NEIGHBOR_EXPLORER_HXX
+
+#include <forward_list>
+
+class Error;
+class NeighborListener;
+struct NeighborInfo;
+
+/**
+ * An object that explores the neighborhood for music servers.
+ *
+ * As soon as this object is opened, it will start exploring, and
+ * notify the #NeighborListener when it found or lost something.
+ *
+ * The implementation is supposed to be non-blocking.  This can be
+ * implemented either using the #EventLoop instance that was passed to
+ * the NeighborPlugin or by moving the blocking parts in a dedicated
+ * thread.
+ */
+class NeighborExplorer {
+protected:
+	NeighborListener &listener;
+
+	explicit NeighborExplorer(NeighborListener &_listener)
+		:listener(_listener) {}
+
+public:
+	typedef std::forward_list<NeighborInfo> List;
+
+	/**
+	 * Free instance data.
+         */
+	virtual ~NeighborExplorer() {}
+
+	/**
+         * Start exploring the neighborhood.
+	 */
+	virtual bool Open(Error &error) = 0;
+
+	/**
+         * Stop exploring.
+	 */
+	virtual void Close() = 0;
+
+	/**
+	 * Obtain a list of currently known neighbors.
+	 */
+	virtual List GetList() const = 0;
+};
+
+#endif
diff --git a/src/neighbor/Glue.cxx b/src/neighbor/Glue.cxx
new file mode 100644
index 000000000..cc0780d58
--- /dev/null
+++ b/src/neighbor/Glue.cxx
@@ -0,0 +1,111 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "Glue.hxx"
+#include "Registry.hxx"
+#include "Explorer.hxx"
+#include "NeighborPlugin.hxx"
+#include "Info.hxx"
+#include "config/ConfigGlobal.hxx"
+#include "config/ConfigData.hxx"
+#include "config/ConfigError.hxx"
+#include "util/Error.hxx"
+
+NeighborGlue::Explorer::~Explorer()
+{
+	delete explorer;
+}
+
+NeighborGlue::~NeighborGlue() {}
+
+static NeighborExplorer *
+CreateNeighborExplorer(EventLoop &loop, NeighborListener &listener,
+		       const config_param &param, Error &error)
+{
+	const char *plugin_name = param.GetBlockValue("plugin");
+	if (plugin_name == nullptr) {
+		error.Set(config_domain,
+			  "Missing \"plugin\" configuration");
+		return nullptr;
+	}
+
+	const NeighborPlugin *plugin = GetNeighborPluginByName(plugin_name);
+	if (plugin == nullptr) {
+		error.Format(config_domain, "No such neighbor plugin: %s",
+			     plugin_name);
+		return nullptr;
+	}
+
+	return plugin->create(loop, listener, param, error);
+}
+
+bool
+NeighborGlue::Init(EventLoop &loop, NeighborListener &listener, Error &error)
+{
+	const config_param *param = nullptr;
+	while ((param = config_get_next_param(CONF_NEIGHBORS, param))) {
+		NeighborExplorer *explorer =
+			CreateNeighborExplorer(loop, listener, *param, error);
+		if (explorer == nullptr) {
+			error.FormatPrefix("Line %i: ", param->line);
+			return false;
+		}
+
+		explorers.emplace_front(explorer);
+	}
+
+	return true;
+}
+
+bool
+NeighborGlue::Open(Error &error)
+{
+	for (auto i = explorers.begin(), end = explorers.end();
+	     i != end; ++i) {
+		if (!i->explorer->Open(error)) {
+			/* roll back */
+			for (auto k = ++i; k != end; ++k)
+				k->explorer->Close();
+			return false;
+		}
+	}
+
+	return true;
+}
+
+void
+NeighborGlue::Close()
+{
+	for (auto i = explorers.begin(), end = explorers.end(); i != end; ++i)
+		i->explorer->Close();
+}
+
+NeighborGlue::List
+NeighborGlue::GetList() const
+{
+	List result;
+
+	for (const auto &i : explorers)
+		result.splice_after(result.before_begin(),
+				    i.explorer->GetList());
+
+	return result;
+}
+
diff --git a/src/neighbor/Glue.hxx b/src/neighbor/Glue.hxx
new file mode 100644
index 000000000..92c612d22
--- /dev/null
+++ b/src/neighbor/Glue.hxx
@@ -0,0 +1,76 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_NEIGHBOR_ALL_HXX
+#define MPD_NEIGHBOR_ALL_HXX
+
+#include "check.h"
+#include "Compiler.h"
+#include "thread/Mutex.hxx"
+
+#include <forward_list>
+
+struct config_param;
+class Error;
+class EventLoop;
+class NeighborExplorer;
+class NeighborListener;
+struct NeighborInfo;
+
+/**
+ * A class that initializes and opens all configured neighbor plugins.
+ */
+class NeighborGlue {
+	struct Explorer {
+		NeighborExplorer *const explorer;
+
+		Explorer(NeighborExplorer *_explorer):explorer(_explorer) {}
+		Explorer(const Explorer &) = delete;
+		~Explorer();
+	};
+
+	Mutex mutex;
+
+	std::forward_list<Explorer> explorers;
+
+public:
+	typedef std::forward_list<NeighborInfo> List;
+
+	NeighborGlue() = default;
+	NeighborGlue(const NeighborGlue &) = delete;
+	~NeighborGlue();
+
+	bool IsEmpty() const {
+		return explorers.empty();
+	}
+
+	bool Init(EventLoop &loop, NeighborListener &listener, Error &error);
+
+	bool Open(Error &error);
+	void Close();
+
+	/**
+	 * Get the combined list of all neighbors from all active
+	 * plugins.
+	 */
+	gcc_pure
+	List GetList() const;
+};
+
+#endif
diff --git a/src/neighbor/Info.hxx b/src/neighbor/Info.hxx
new file mode 100644
index 000000000..3a34896e7
--- /dev/null
+++ b/src/neighbor/Info.hxx
@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_NEIGHBOR_INFO_HXX
+#define MPD_NEIGHBOR_INFO_HXX
+
+#include <string>
+
+struct NeighborInfo {
+	std::string uri;
+	std::string display_name;
+};
+
+#endif
diff --git a/src/neighbor/Listener.hxx b/src/neighbor/Listener.hxx
new file mode 100644
index 000000000..20295f5a9
--- /dev/null
+++ b/src/neighbor/Listener.hxx
@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_NEIGHBOR_LISTENER_HXX
+#define MPD_NEIGHBOR_LISTENER_HXX
+
+struct NeighborInfo;
+class NeighborExplorer;
+
+/**
+ * An interface that listens on events from neighbor plugins.  The
+ * methods must be thread-safe and non-blocking.
+ */
+class NeighborListener {
+public:
+	virtual void FoundNeighbor(const NeighborInfo &info) = 0;
+	virtual void LostNeighbor(const NeighborInfo &info) = 0;
+};
+
+#endif
diff --git a/src/neighbor/NeighborPlugin.hxx b/src/neighbor/NeighborPlugin.hxx
new file mode 100644
index 000000000..0d4ebaa7b
--- /dev/null
+++ b/src/neighbor/NeighborPlugin.hxx
@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_NEIGHBOR_PLUGIN_HXX
+#define MPD_NEIGHBOR_PLUGIN_HXX
+
+struct config_param;
+class Error;
+class EventLoop;
+class NeighborListener;
+class NeighborExplorer;
+
+struct NeighborPlugin {
+	const char *name;
+
+	/**
+	 * Allocates and configures a #NeighborExplorer instance.
+	 */
+	NeighborExplorer *(*create)(EventLoop &loop, NeighborListener &listener,
+				    const config_param &param,
+				    Error &error);
+};
+
+#endif
diff --git a/src/neighbor/Registry.cxx b/src/neighbor/Registry.cxx
new file mode 100644
index 000000000..fc9d05ecf
--- /dev/null
+++ b/src/neighbor/Registry.cxx
@@ -0,0 +1,42 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "Registry.hxx"
+#include "NeighborPlugin.hxx"
+#include "plugins/SmbclientNeighborPlugin.hxx"
+
+#include <string.h>
+
+const NeighborPlugin *const neighbor_plugins[] = {
+#ifdef ENABLE_SMBCLIENT
+	&smbclient_neighbor_plugin,
+#endif
+	nullptr
+};
+
+const NeighborPlugin *
+GetNeighborPluginByName(const char *name)
+{
+	for (auto i = neighbor_plugins; *i != nullptr; ++i)
+		if (strcmp((*i)->name, name) == 0)
+			return *i;
+
+	return nullptr;
+}
diff --git a/src/neighbor/Registry.hxx b/src/neighbor/Registry.hxx
new file mode 100644
index 000000000..0b89e537d
--- /dev/null
+++ b/src/neighbor/Registry.hxx
@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_NEIGHBOR_REGISTRY_HXX
+#define MPD_NEIGHBOR_REGISTRY_HXX
+
+#include "Compiler.h"
+
+struct NeighborPlugin;
+
+/**
+ * nullptr terminated list of all neighbor plugins which were enabled at
+ * compile time.
+ */
+extern const NeighborPlugin *const neighbor_plugins[];
+
+gcc_pure
+const NeighborPlugin *
+GetNeighborPluginByName(const char *name);
+
+#endif
diff --git a/src/neighbor/plugins/SmbclientNeighborPlugin.cxx b/src/neighbor/plugins/SmbclientNeighborPlugin.cxx
new file mode 100644
index 000000000..8dc537e94
--- /dev/null
+++ b/src/neighbor/plugins/SmbclientNeighborPlugin.cxx
@@ -0,0 +1,285 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "SmbclientNeighborPlugin.hxx"
+#include "lib/smbclient/Init.hxx"
+#include "neighbor/NeighborPlugin.hxx"
+#include "neighbor/Explorer.hxx"
+#include "neighbor/Listener.hxx"
+#include "neighbor/Info.hxx"
+#include "thread/Mutex.hxx"
+#include "thread/Cond.hxx"
+#include "thread/Thread.hxx"
+#include "thread/Name.hxx"
+#include "util/Macros.hxx"
+#include "util/Domain.hxx"
+#include "util/Error.hxx"
+#include "Log.hxx"
+
+#include <libsmbclient.h>
+
+#include <list>
+#include <algorithm>
+
+static constexpr Domain smbclient_domain("smbclient");
+
+class SmbclientNeighborExplorer final : public NeighborExplorer {
+	struct Server {
+		std::string name, comment;
+
+		bool alive;
+
+		Server(std::string &&_name, std::string &&_comment)
+			:name(std::move(_name)), comment(std::move(_comment)),
+			 alive(true) {}
+		Server(const Server &) = delete;
+
+		gcc_pure
+		bool operator==(const Server &other) const {
+			return name == other.name;
+		}
+
+		gcc_pure
+		NeighborInfo Export() const {
+			return { "smb://" + name + "/", comment };
+		}
+	};
+
+	Thread thread;
+
+	mutable Mutex mutex;
+	Cond cond;
+
+	List list;
+
+	bool quit;
+
+public:
+	SmbclientNeighborExplorer(NeighborListener &_listener)
+		:NeighborExplorer(_listener) {}
+
+	/* virtual methods from class NeighborExplorer */
+	virtual bool Open(Error &error) override;
+	virtual void Close() override;
+	virtual List GetList() const override;
+
+private:
+	void Run();
+	void ThreadFunc();
+	static void ThreadFunc(void *ctx);
+};
+
+bool
+SmbclientNeighborExplorer::Open(Error &error)
+{
+	quit = false;
+	return thread.Start(ThreadFunc, this, error);
+}
+
+void
+SmbclientNeighborExplorer::Close()
+{
+	mutex.lock();
+	quit = true;
+	cond.signal();
+	mutex.unlock();
+
+	thread.Join();
+}
+
+NeighborExplorer::List
+SmbclientNeighborExplorer::GetList() const
+{
+	const ScopeLock protect(mutex);
+	/*
+	List list;
+	for (const auto &i : servers)
+		list.emplace_front(i.Export());
+	*/
+	return list;
+}
+
+static void
+ReadServer(NeighborExplorer::List &list, const smbc_dirent &e)
+{
+	const std::string name(e.name, e.namelen);
+	const std::string comment(e.comment, e.commentlen);
+
+	NeighborInfo info{
+		"smb://" + name,
+		name + " (" + comment + ")",
+	};
+
+	list.emplace_front(std::move(info));
+}
+
+static void
+ReadServers(NeighborExplorer::List &list, const char *uri);
+
+static void
+ReadWorkgroup(NeighborExplorer::List &list, const std::string &name)
+{
+	std::string uri = "smb://" + name;
+	ReadServers(list, uri.c_str());
+}
+
+static void
+ReadEntry(NeighborExplorer::List &list, const smbc_dirent &e)
+{
+	switch (e.smbc_type) {
+	case SMBC_WORKGROUP:
+		ReadWorkgroup(list, std::string(e.name, e.namelen));
+		break;
+
+	case SMBC_SERVER:
+		ReadServer(list, e);
+		break;
+	}
+}
+
+static void
+ReadServers(NeighborExplorer::List &list, int fd)
+{
+	smbc_dirent *e;
+	while ((e = smbc_readdir(fd)) != nullptr)
+		ReadEntry(list, *e);
+
+	smbc_closedir(fd);
+}
+
+static void
+ReadServers(NeighborExplorer::List &list, const char *uri)
+{
+	int fd = smbc_opendir(uri);
+	if (fd >= 0) {
+		ReadServers(list, fd);
+		smbc_closedir(fd);
+	} else
+		FormatErrno(smbclient_domain, "smbc_opendir('%s') failed",
+			    uri);
+}
+
+gcc_pure
+static NeighborExplorer::List
+DetectServers()
+{
+	NeighborExplorer::List list;
+	ReadServers(list, "smb://");
+	return list;
+}
+
+gcc_pure
+static NeighborExplorer::List::const_iterator
+FindBeforeServerByURI(NeighborExplorer::List::const_iterator prev,
+		      NeighborExplorer::List::const_iterator end,
+		      const std::string &uri)
+{
+	for (auto i = std::next(prev); i != end; prev = i, i = std::next(prev))
+		if (i->uri == uri)
+			return prev;
+
+	return end;
+}
+
+inline void
+SmbclientNeighborExplorer::Run()
+{
+	List found = DetectServers(), lost;
+
+	mutex.lock();
+
+	const auto found_before_begin = found.before_begin();
+	const auto found_end = found.end();
+
+	for (auto prev = list.before_begin(), i = std::next(prev), end = list.end();
+	     i != end; i = std::next(prev)) {
+		auto f = FindBeforeServerByURI(found_before_begin, found_end,
+					       i->uri);
+		if (f != found_end) {
+			/* still visible: remove from "found" so we
+			   don't believe it's a new one */
+			*i = std::move(*std::next(f));
+			found.erase_after(f);
+			prev = i;
+		} else {
+			/* can't see it anymore: move to "lost" */
+			lost.splice_after(lost.before_begin(), list, prev);
+		}
+	}
+
+	for (auto prev = found_before_begin, i = std::next(prev);
+	     i != found_end; prev = i, i = std::next(prev))
+		list.push_front(*i);
+
+	mutex.unlock();
+
+	for (auto &i : lost)
+		listener.LostNeighbor(i);
+
+	for (auto &i : found)
+		listener.FoundNeighbor(i);
+}
+
+inline void
+SmbclientNeighborExplorer::ThreadFunc()
+{
+	mutex.lock();
+
+	while (!quit) {
+		mutex.unlock();
+
+		Run();
+
+		mutex.lock();
+		if (quit)
+			break;
+
+		// TODO: sleep for how long?
+		cond.timed_wait(mutex, 10000);
+	}
+
+	mutex.unlock();
+}
+
+void
+SmbclientNeighborExplorer::ThreadFunc(void *ctx)
+{
+	SetThreadName("smbclient");
+
+	SmbclientNeighborExplorer &e = *(SmbclientNeighborExplorer *)ctx;
+	e.ThreadFunc();
+}
+
+static NeighborExplorer *
+smbclient_neighbor_create(gcc_unused EventLoop &loop,
+			  NeighborListener &listener,
+			  gcc_unused const config_param &param,
+			  gcc_unused Error &error)
+{
+	if (!SmbclientInit(error))
+		return nullptr;
+
+	return new SmbclientNeighborExplorer(listener);
+}
+
+const NeighborPlugin smbclient_neighbor_plugin = {
+	"smbclient",
+	smbclient_neighbor_create,
+};
diff --git a/src/neighbor/plugins/SmbclientNeighborPlugin.hxx b/src/neighbor/plugins/SmbclientNeighborPlugin.hxx
new file mode 100644
index 000000000..12ec9c0cd
--- /dev/null
+++ b/src/neighbor/plugins/SmbclientNeighborPlugin.hxx
@@ -0,0 +1,27 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_NEIGHBOR_SMBCLIENT_HXX
+#define MPD_NEIGHBOR_SMBCLIENT_HXX
+
+struct NeighborPlugin;
+
+extern const NeighborPlugin smbclient_neighbor_plugin;
+
+#endif