diff --git a/src/ebusd/bushandler.cpp b/src/ebusd/bushandler.cpp
index b6e9eeb6..836c6483 100644
--- a/src/ebusd/bushandler.cpp
+++ b/src/ebusd/bushandler.cpp
@@ -733,6 +733,16 @@ void BusHandler::receiveCompleted()
 			logNotice(lf_update, "unknown MM cmd: %s", m_command.getDataStr().c_str());
 		else
 			logNotice(lf_update, "unknown MS cmd: %s / %s", m_command.getDataStr().c_str(), m_response.getDataStr().c_str());
+
+		if (m_grabUnknownMessages) {
+			string data;
+			string key = data = m_command.getDataStr();
+			if (key.length() > 2*(1+1+2+1+4))
+				key = key.substr(0, 2*(1+1+2+1+4)); // QQZZPBSBNN + up to 4 DD bytes
+			if (dstAddress != BROADCAST && !master)
+				data += " / " + m_response.getDataStr();
+			m_grabbedUnknownMessages[key] = data;
+		}
 	}
 	else {
 		string circuit = message->getCircuit();
@@ -816,3 +826,25 @@ void BusHandler::formatScanResult(ostringstream& output)
 		}
 	}
 }
+
+void BusHandler::enableGrab(bool enable)
+{
+	m_grabUnknownMessages = enable;
+	m_grabbedUnknownMessages.clear();
+}
+
+void BusHandler::formatGrabResult(ostringstream& output)
+{
+	if (!m_grabUnknownMessages) {
+		output << "grab disabled";
+	} else {
+		bool first = true;
+		for (map<string, string>::iterator it = m_grabbedUnknownMessages.begin(); it != m_grabbedUnknownMessages.end(); it++) {
+			if (first)
+				first = false;
+			else
+				output << endl;
+			output << it->second;
+		}
+	}
+}
diff --git a/src/ebusd/bushandler.h b/src/ebusd/bushandler.h
index 021ef1ad..002f54d8 100644
--- a/src/ebusd/bushandler.h
+++ b/src/ebusd/bushandler.h
@@ -279,7 +279,7 @@ public:
 		  m_symPerSec(0), m_maxSymPerSec(0),
 		  m_state(bs_noSignal), m_repeat(false),
 		  m_command(false), m_commandCrcValid(false), m_response(false), m_responseCrcValid(false),
-		  m_scanMessage(NULL) {
+		  m_scanMessage(NULL), m_grabUnknownMessages(false) {
 		memset(m_seenAddresses, 0, sizeof(m_seenAddresses));
 	}
 
@@ -318,6 +318,18 @@ public:
 	 */
 	void formatScanResult(ostringstream& output);
 
+	/**
+	 * Start or stop grabbing unknown messages.
+	 * @param enable true to enable grabbing, false to disable it.
+	 */
+	void enableGrab(bool enable=true);
+
+	/**
+	 * Format the grabbed unknown messages to the @a ostringstream.
+	 * @param output the @a ostringstream to format the messages to.
+	 */
+	void formatGrabResult(ostringstream& output);
+
 	/**
 	 * Return true when a signal on the bus is available.
 	 * @return true when a signal on the bus is available.
@@ -461,6 +473,12 @@ private:
 	/** the scan results by slave address. */
 	map<unsigned char, string> m_scanResults;
 
+	/** whether to grab unknown messages. */
+	bool m_grabUnknownMessages;
+
+	/** the grabbed unknown messages by ID prefix (QQZZPBSBNNDD with up to 4 DD bytes).*/
+	map<string, string> m_grabbedUnknownMessages;
+
 };
 
 
diff --git a/src/ebusd/mainloop.cpp b/src/ebusd/mainloop.cpp
index e3507c13..fa6c37b0 100644
--- a/src/ebusd/mainloop.cpp
+++ b/src/ebusd/mainloop.cpp
@@ -101,7 +101,10 @@ void MainLoop::run()
 			result = decodeMessage(data, connected, listening, running);
 
 			logNotice(lf_main, "<<< %s", result.c_str());
-			result += "\n\n";
+			if (result.length() == 0)
+				result = "\n";
+			else
+				result += "\n\n";
 		}
 		if (listening) {
 			result += getUpdates(since, until);
@@ -167,6 +170,8 @@ string MainLoop::decodeMessage(const string& data, bool& connected, bool& listen
 		return executeListen(args, listening);
 	if (strcasecmp(str, "S") == 0 || strcasecmp(str, "STATE") == 0)
 		return executeState(args);
+	if (strcasecmp(str, "G") == 0 || strcasecmp(str, "GRAB") == 0)
+		return executeGrab(args);
 	if (strcasecmp(str, "SCAN") == 0)
 		return executeScan(args);
 	if (strcasecmp(str, "LOG") == 0)
@@ -590,6 +595,31 @@ string MainLoop::executeState(vector<string> &args)
 	return "no signal";
 }
 
+string MainLoop::executeGrab(vector<string> &args)
+{
+	if (args.size() == 1) {
+		m_busHandler->enableGrab();
+
+		return getResultCode(RESULT_OK);
+	}
+
+	if (args.size() == 2 && strcasecmp(args[1].c_str(), "STOP") == 0) {
+		m_busHandler->enableGrab(false);
+
+		return getResultCode(RESULT_OK);
+	}
+
+	if (args.size() == 2 && strcasecmp(args[1].c_str(), "RESULT") == 0) {
+		ostringstream result;
+		m_busHandler->formatGrabResult(result);
+		return result.str();
+	}
+
+	return "usage: grab [stop]\n"
+		   "  or:  grab result\n"
+		   " Grab unknown messages or stop it, or report the seen unknown messages.";
+}
+
 string MainLoop::executeScan(vector<string> &args)
 {
 	if (args.size() == 1) {
@@ -699,24 +729,26 @@ string MainLoop::executeQuit(vector<string> &args, bool& connected)
 string MainLoop::executeHelp()
 {
 	return "usage:\n"
-		   " read|r   Read value(s):        read [-v] [-f] [-m SECONDS] [-d ZZ] [-c CIRCUIT] NAME [FIELD[.N]]\n"
-		   " write|w  Write value(s):       write [-c] CIRCUIT NAME [VALUE[;VALUE]*]\n"
-		   "          Write hex message:    write -h ZZPBSBNNDx'\n"
-		   " find|f   Find message(s):      find [-v] [-r] [-w] [-p] [-d] [-i PB] [-f] [-c CIRCUIT] [NAME]\n"
-		   " listen|l Listen for updates:   listen [stop]\n"
+		   " read|r   Read value(s):         read [-v] [-f] [-m SECONDS] [-d ZZ] [-c CIRCUIT] NAME [FIELD[.N]]\n"
+		   " write|w  Write value(s):        write [-c] CIRCUIT NAME [VALUE[;VALUE]*]\n"
+		   "          Write hex message:     write -h ZZPBSBNNDx'\n"
+		   " find|f   Find message(s):       find [-v] [-r] [-w] [-p] [-d] [-i PB] [-f] [-c CIRCUIT] [NAME]\n"
+		   " listen|l Listen for updates:    listen [stop]\n"
 		   " state|s  Report bus state\n"
-		   " scan     Scan slaves:          scan [full]\n"
-		   "          Report scan result:   scan result\n"
-		   " log      Set log area(s):      log areas AREA[,AREA*]\n"
-		   "                                  AREA: main|network|bus|update|all\n"
-		   "          Set log level:        log level LEVEL\n"
-		   "                                  LEVEL: error|notice|info|debug\n"
+		   " grab|g   Grab unknown messages: grab [stop]\n"
+		   "          Report the messages:   grab result\n"
+		   " scan     Scan slaves:           scan [full]\n"
+		   "          Report scan result:    scan result\n"
+		   " log      Set log area(s):       log areas AREA[,AREA*]\n"
+		   "                                   AREA: main|network|bus|update|all\n"
+		   "          Set log level:         log level LEVEL\n"
+		   "                                   LEVEL: error|notice|info|debug\n"
 		   " raw      Toggle logging raw bytes\n"
 		   " dump     Toggle dumping raw bytes\n"
 		   " reload   Reload CSV config files\n"
 		   " stop     Stop the daemon\n"
 		   " quit|q   Close connection\n"
-		   " help|h   Print help            help [COMMAND]";
+		   " help|h   Print help             help [COMMAND]";
 }
 
 string MainLoop::getUpdates(time_t since, time_t until)
diff --git a/src/ebusd/mainloop.h b/src/ebusd/mainloop.h
index 96310c2f..4b26b636 100644
--- a/src/ebusd/mainloop.h
+++ b/src/ebusd/mainloop.h
@@ -129,6 +129,13 @@ private:
 	 */
 	string executeState(vector<string> &args);
 
+	/**
+	 * Execute the grab command.
+	 * @param args the arguments passed to the command (starting with the command itself), or empty for help.
+	 * @return the result string.
+	 */
+	string executeGrab(vector<string> &args);
+
 	/**
 	 * Execute the scan command.
 	 * @param args the arguments passed to the command (starting with the command itself), or empty for help.