diff --git a/qse/include/qse/si/App.hpp b/qse/include/qse/si/App.hpp
index a4729bd4..ba04c568 100644
--- a/qse/include/qse/si/App.hpp
+++ b/qse/include/qse/si/App.hpp
@@ -53,6 +53,23 @@ public:
 
 	virtual void on_signal (int sig) { }
 
+	int subscribeToSignal (int sig, bool accept);
+	void unsubscribeFromSignal (int sig);
+
+	typedef void (*SignalHandler) (int sig);
+	static qse_size_t _sighrs[2][QSE_NSIGS];
+
+	// You may set a global signal handler with setSignalHandler().
+	// If an application is subscribing to a single with subscribeToSignal(),
+	// this function is doomed to fail. If a successful call to 
+	// setSignalHandler() has been made withoutut unsetSingalHandler() called
+	// yet, a subsequence call to subscribeToSignal() is doomed to fail too.
+	// These two different interfaces are mutually exclusive.
+	static int setSignalHandler (int sig, SignalHandler sighr);
+	static int unsetSignalHandler (int sig);
+
+	int guardProcess (const qse_mchar_t* proc_name);
+
 protected:
 	bool _root_only;
 
@@ -78,21 +95,6 @@ public:
 
 	_SigLink _sig[QSE_NSIGS]; 
 
-	typedef void (*SignalHandler) (int sig);
-	static qse_size_t _sighrs[2][QSE_NSIGS];
-
-	int subscribeToSignal (int sig, bool accept);
-	void unsubscribeFromSignal (int sig);
-
-	// You may set a global signal handler with setSignalHandler().
-	// If an application is subscribing to a single with subscribeToSignal(),
-	// this function is doomed to fail. If a successful call to 
-	// setSignalHandler() has been made withoutut unsetSingalHandler() called
-	// yet, a subsequence call to subscribeToSignal() is doomed to fail too.
-	// These two different interfaces are mutually exclusive.
-	static int setSignalHandler (int sig, SignalHandler sighr);
-	static int unsetSignalHandler (int sig);
-
 protected:
 	static int set_signal_handler_no_mutex (int sig, SignalHandler sighr);
 	static int unset_signal_handler_no_mutex (int sig);
diff --git a/qse/lib/si/App.cpp b/qse/lib/si/App.cpp
index 491c2821..e662480d 100644
--- a/qse/lib/si/App.cpp
+++ b/qse/lib/si/App.cpp
@@ -382,6 +382,27 @@ void App::unsubscribe_from_all_signals_no_mutex()
 	}
 }
 
+int App::guardProcess (const qse_mchar_t* proc_name)
+{
+// TODO: enhance it
+	while (1)
+	{
+		pid_t pid = ::fork();
+		if (pid == -1) return -1;
+		if (pid == 0) break; // child
+
+		int status;
+		while (::waitpid(pid, &status, 0) != pid);
+		if (WIFEXITED(status) && WEXITSTATUS(status) == 0) 
+		{
+			return 0;
+		}
+	}
+
+	// TODO: if (proc_name) qse_set_proc_name (proc_name);
+	return 1; // the caller must execute the actual work.
+}
+
 /////////////////////////////////
 QSE_END_NAMESPACE(QSE)
 /////////////////////////////////
diff --git a/qse/lib/si/os.c b/qse/lib/si/os.c
index 7be851e6..b28bd0ca 100644
--- a/qse/lib/si/os.c
+++ b/qse/lib/si/os.c
@@ -53,3 +53,10 @@ void qse_sleep (const qse_ntime_t* interval)
 #endif
 }
 
+/*
+ TODO:
+int qse_set_proc_name (const qse_char_t* name)
+{
+	::prctl(PR_SET_NAME, name, 0, 0, 0);
+}*/
+
diff --git a/qse/samples/si/tcpsvr01.cpp b/qse/samples/si/tcpsvr01.cpp
index d13ba10d..66e8b1f7 100644
--- a/qse/samples/si/tcpsvr01.cpp
+++ b/qse/samples/si/tcpsvr01.cpp
@@ -3,6 +3,7 @@
 #include <qse/si/sio.h>
 #include <qse/si/os.h>
 #include <qse/cmn/mem.h>
+#include <qse/cmn/str.h>
 #include <qse/cmn/HeapMmgr.hpp>
 #include <qse/si/App.hpp>
 
@@ -12,10 +13,14 @@
 #	include <windows.h>
 #endif
 
-#include <unistd.h>
 #include <signal.h>
 #include <string.h>
 
+
+#include <sys/wait.h>
+#include <sys/prctl.h>
+#include <unistd.h>
+
 class ClientHandler
 {
 public:
@@ -70,8 +75,13 @@ public:
 
 	int run ()
 	{
-		this->server.setThreadStackSize (256000);
-		return this->server.start (QSE_T("[::]:9998,0.0.0.0:9998"));
+		if (this->guardProcess("myapp") > 0)
+		{
+qse_printf (QSE_T("Stareting workd\n"));
+			this->server.setThreadStackSize (256000);
+			return this->server.start (QSE_T("[::]:9998,0.0.0.0:9998"));
+		}
+		return -1;
 	}
 
 protected:
@@ -87,7 +97,7 @@ MyApp app2 (&heap_mmgr);
 MyApp app3 (&heap_mmgr);
 MyApp app4 (&heap_mmgr);
 
-	app.subscribeToSignal (SIGINT, true)	;
+	app.subscribeToSignal (SIGINT, true);
 	app.subscribeToSignal (SIGTERM, true);
 
 app4.subscribeToSignal (SIGINT, true); 
@@ -205,7 +215,7 @@ int main ()
 	}
 	else
 	{
-		sprintf (locale, ".%u", (unsigned int)codepage);
+		qse_mbsxfmt (locale, QSE_COUNTOF(locale), ".%u", (unsigned int)codepage);
 		setlocale (LC_ALL, locale);
 		/*qse_setdflcmgrbyid (QSE_CMGR_SLMB);*/
 	}
diff --git a/qse/samples/si/tcpsvr02.cpp b/qse/samples/si/tcpsvr02.cpp
index bc229630..fa69d73a 100644
--- a/qse/samples/si/tcpsvr02.cpp
+++ b/qse/samples/si/tcpsvr02.cpp
@@ -3,6 +3,7 @@
 #include <qse/si/sio.h>
 #include <qse/si/os.h>
 #include <qse/cmn/mem.h>
+#include <qse/cmn/str.h>
 #include <qse/cmn/HeapMmgr.hpp>
 #include <qse/sttp/Sttp.hpp>
 #include <qse/si/App.hpp>
@@ -130,7 +131,7 @@ int main ()
 	}
 	else
 	{
-		sprintf (locale, ".%u", (unsigned int)codepage);
+		qse_mbsxfmt (locale, QSE_COUNTOF(locale), ".%u", (unsigned int)codepage);
 		setlocale (LC_ALL, locale);
 		/*qse_setdflcmgrbyid (QSE_CMGR_SLMB);*/
 	}