diff --git a/gui/CMakeLists.txt b/gui/CMakeLists.txt
index 70b5072..73d61f7 100644
--- a/gui/CMakeLists.txt
+++ b/gui/CMakeLists.txt
@@ -12,7 +12,9 @@ add_executable(chiaki
 		include/streamwindow.h
 		src/streamwindow.cpp
 		include/videodecoder.h
-		src/videodecoder.cpp)
+		src/videodecoder.cpp
+		include/discoverycmd.h
+		src/discoverycmd.cpp)
 target_include_directories(chiaki PRIVATE include)
 
 target_link_libraries(chiaki chiaki-lib)
diff --git a/gui/include/discoverycmd.h b/gui/include/discoverycmd.h
new file mode 100644
index 0000000..5451b8d
--- /dev/null
+++ b/gui/include/discoverycmd.h
@@ -0,0 +1,25 @@
+/*
+ * This file is part of Chiaki.
+ *
+ * Chiaki 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 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Chiaki 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 Chiaki.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef CHIAKI_DISCOVERYCMD_H
+#define CHIAKI_DISCOVERYCMD_H
+
+#include <QString>
+
+int RunDiscoveryCmd(const QString &host);
+
+#endif //CHIAKI_DISCOVERYCMD_H
diff --git a/gui/src/discoverycmd.cpp b/gui/src/discoverycmd.cpp
new file mode 100644
index 0000000..1701f3f
--- /dev/null
+++ b/gui/src/discoverycmd.cpp
@@ -0,0 +1,93 @@
+/*
+ * This file is part of Chiaki.
+ *
+ * Chiaki 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 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Chiaki 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 Chiaki.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <discoverycmd.h>
+
+#include <chiaki/log.h>
+#include <chiaki/discovery.h>
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netdb.h>
+#include <unistd.h>
+#include <netdb.h>
+
+
+int RunDiscoveryCmd(const QString &host)
+{
+	ChiakiLog log;
+
+	ChiakiDiscovery discovery;
+	ChiakiErrorCode err = chiaki_discovery_init(&discovery, &log, AF_INET); // TODO: IPv6
+	if(err != CHIAKI_ERR_SUCCESS)
+	{
+		CHIAKI_LOGE(&log, "Discovery init failed\n");
+		return 1;
+	}
+
+	ChiakiDiscoveryThread thread;
+	err = chiaki_discovery_thread_start(&thread, &discovery);
+	if(err != CHIAKI_ERR_SUCCESS)
+	{
+		CHIAKI_LOGE(&log, "Discovery thread init failed\n");
+		chiaki_discovery_fini(&discovery);
+		return 1;
+	}
+
+	struct addrinfo *host_addrinfos;
+	int r = getaddrinfo(host.toUtf8().constData(), NULL, NULL, &host_addrinfos);
+	if(r != 0)
+	{
+		CHIAKI_LOGE(&log, "getaddrinfo failed\n");
+		return 1;
+	}
+
+	struct sockaddr *host_addr = nullptr;
+	socklen_t host_addr_len = 0;
+	for(struct addrinfo *ai=host_addrinfos; ai; ai=ai->ai_next)
+	{
+		if(ai->ai_protocol != IPPROTO_UDP)
+			continue;
+		if(ai->ai_family != AF_INET) // TODO: IPv6
+			continue;
+
+		host_addr_len = ai->ai_addrlen;
+		host_addr = (struct sockaddr *)malloc(host_addr_len);
+		if(!host_addr)
+			break;
+		memcpy(host_addr, ai->ai_addr, host_addr_len);
+	}
+	freeaddrinfo(host_addrinfos);
+
+	if(!host_addr)
+		CHIAKI_LOGE(&log, "Failed to get addr for hostname\n");
+	else
+	{
+		((struct sockaddr_in *)host_addr)->sin_port = htons(CHIAKI_DISCOVERY_PORT); // TODO: IPv6
+
+		ChiakiDiscoveryPacket packet;
+		memset(&packet, 0, sizeof(packet));
+		packet.cmd = CHIAKI_DISCOVERY_CMD_SRCH;
+
+		chiaki_discovery_send(&discovery, &packet, host_addr, host_addr_len);
+	}
+
+	while(1)
+		sleep(1);
+
+	return 0;
+}
\ No newline at end of file
diff --git a/gui/src/main.cpp b/gui/src/main.cpp
index 5da505c..2948d07 100644
--- a/gui/src/main.cpp
+++ b/gui/src/main.cpp
@@ -1,6 +1,7 @@
 
 #include <streamwindow.h>
 #include <videodecoder.h>
+#include <discoverycmd.h>
 
 #include <chiaki/session.h>
 #include <chiaki/base64.h>
@@ -11,6 +12,66 @@
 #include <QApplication>
 #include <QAudioOutput>
 #include <QAudioFormat>
+#include <QCommandLineParser>
+
+
+int RunStream(QApplication &app, const QString &host, const QString &registkey, const QString &ostype, const QString &auth, const QString &morning, const QString &did);
+
+int main(int argc, char *argv[])
+{
+	QApplication app(argc, argv);
+	QApplication::setApplicationName("Chiaki");
+
+	QCommandLineParser parser;
+	parser.addHelpOption();
+
+	parser.addPositionalArgument("command", "Command");
+	parser.addPositionalArgument("host", "Host");
+
+	QCommandLineOption regist_key_option("registkey");
+	parser.addOption(regist_key_option);
+
+	QCommandLineOption ostype_option("ostype", "Win10.0.0");
+	parser.addOption(ostype_option);
+
+	QCommandLineOption auth_option("auth");
+	parser.addOption(auth_option);
+
+	QCommandLineOption morning_option("morning");
+	parser.addOption(morning_option);
+
+	QCommandLineOption did_option("did");
+	parser.addOption(did_option);
+
+
+	parser.process(app);
+	QStringList args = parser.positionalArguments();
+
+	if(args.length() < 2)
+		parser.showHelp(1);
+
+	QString host = args[1];
+
+	if(args[0] == "stream")
+	{
+		QString registkey = parser.value(regist_key_option);
+		QString ostype = parser.value(ostype_option);
+		QString auth = parser.value(auth_option);
+		QString morning = parser.value(morning_option);
+		QString did = parser.value(did_option);
+		if(registkey.isEmpty() || ostype.isEmpty() || auth.isEmpty() || morning.isEmpty() || did.isEmpty())
+			parser.showHelp(1);
+		return RunStream(app, host, registkey, ostype, auth, morning, did);
+	}
+	else if(args[0] == "discover")
+	{
+		return RunDiscoveryCmd(args[1]);
+	}
+	else
+	{
+		parser.showHelp(1);
+	}
+}
 
 
 QAudioOutput *audio_out;
@@ -38,28 +99,28 @@ void video_sample_cb(uint8_t *buf, size_t buf_size, void *user)
 }
 
 
-int main(int argc, char *argv[])
+int RunStream(QApplication &app, const QString &host, const QString &registkey, const QString &ostype, const QString &auth, const QString &morning, const QString &did)
 {
-	if(argc != 7)
-	{
-		printf("Usage: %s <host> <registkey> <ostype> <auth> <morning (base64)> <did>\n", argv[0]);
-		return 1;
-	}
+	QByteArray host_str = host.toUtf8();
+	QByteArray registkey_str = registkey.toUtf8();
+	QByteArray ostype_str = ostype.toUtf8();
 
 	ChiakiConnectInfo connect_info;
-	connect_info.host = argv[1];
-	connect_info.regist_key = argv[2];
-	connect_info.ostype = argv[3];
+	connect_info.host = host_str.constData();
+	connect_info.regist_key = registkey_str.constData();
+	connect_info.ostype = ostype_str.constData();
 
-	size_t auth_len = strlen(argv[4]);
+	QByteArray auth_str = auth.toUtf8();
+	size_t auth_len = auth_str.length();
 	if(auth_len > sizeof(connect_info.auth))
 		auth_len = sizeof(connect_info.auth);
-	memcpy(connect_info.auth, argv[4], auth_len);
+	memcpy(connect_info.auth, auth_str.constData(), auth_len);
 	if(auth_len < sizeof(connect_info.auth))
 		memset(connect_info.auth + auth_len, 0, sizeof(connect_info.auth) - auth_len);
 
 	size_t morning_size = sizeof(connect_info.morning);
-	ChiakiErrorCode err = chiaki_base64_decode(argv[5], strlen(argv[5]), connect_info.morning, &morning_size);
+	QByteArray morning_str = morning.toUtf8();
+	ChiakiErrorCode err = chiaki_base64_decode(morning_str.constData(), morning_str.length(), connect_info.morning, &morning_size);
 	if(err != CHIAKI_ERR_SUCCESS || morning_size != sizeof(connect_info.morning))
 	{
 		printf("morning invalid.\n");
@@ -67,16 +128,14 @@ int main(int argc, char *argv[])
 	}
 
 	size_t did_size = sizeof(connect_info.did);
-	err = chiaki_base64_decode(argv[6], strlen(argv[6]), connect_info.did, &did_size);
+	QByteArray did_str = did.toUtf8();
+	err = chiaki_base64_decode(did_str.constData(), did_str.length(), connect_info.did, &did_size);
 	if(err != CHIAKI_ERR_SUCCESS || did_size != sizeof(connect_info.did))
 	{
 		printf("did invalid.\n");
 		return 1;
 	}
 
-	argc = 1;
-	QApplication app(argc, argv);
-
 	StreamWindow window;
 	window.resize(640, 360);
 	window.show();
@@ -136,6 +195,5 @@ int main(int argc, char *argv[])
 
 	delete audio_out;
 
-
-	return ret;
-}
\ No newline at end of file
+	return 0;
+}