diff --git a/include/villas/dumper.hpp b/include/villas/dumper.hpp
index 6e0482454..4d8bfd225 100644
--- a/include/villas/dumper.hpp
+++ b/include/villas/dumper.hpp
@@ -21,6 +21,8 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *********************************************************************************/
 
+#pragma once
+
 #include <string>
 
 namespace villas {
@@ -37,8 +39,10 @@ protected:
 public:
 	Dumper(const std::string &socketNameIn);
 	~Dumper();
+
 	int openSocket();
-	void closeSocket();
+	int closeSocket();
+
 	void writeData(uint len, double *yData, double *xData = nullptr);
 };
 
diff --git a/lib/dumper.cpp b/lib/dumper.cpp
index c70ec4035..4bbabc191 100644
--- a/lib/dumper.cpp
+++ b/lib/dumper.cpp
@@ -20,13 +20,16 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *********************************************************************************/
 
-#include <villas/dumper.hpp>
 #include <sys/socket.h>
 #include <sys/types.h>
 #include <sys/un.h>
-#include <villas/log.h>
 #include <unistd.h>
 
+#include <sstream>
+
+#include <villas/dumper.hpp>
+#include <villas/log.h>
+
 using namespace villas;
 using namespace villas::node;
 
@@ -54,28 +57,37 @@ int Dumper::openSocket()
 	socketaddrUn.sun_family = AF_UNIX;
 	strcpy(socketaddrUn.sun_path, socketName.c_str());
 
-	connect(socketFd, (struct sockaddr *) &socketaddrUn, sizeof(socketaddrUn));
+	int ret = connect(socketFd, (struct sockaddr *) &socketaddrUn, sizeof(socketaddrUn));
+	if (!ret)
+		return ret;
 
-	return 1;
+	return 0;
 }
 
-void Dumper::closeSocket()
+int Dumper::closeSocket()
 {
-	close(socketFd);
+	int ret = close(socketFd);
+	if (!ret)
+		return ret;
+
+	return 0;
 }
 
 void Dumper::writeData(unsigned len, double *yData, double *xData)
 {
-	ssize_t bytesWritten;
-
 	for (unsigned i = 0; i<len; i++) {
-		std::string str = std::to_string(yData[i]);
-		if(xData != nullptr)
-			str+= ";" + std::to_string(xData[i]);
-		str += "\n";
+		std::stringstream ss;
 
-		bytesWritten =  write(socketFd, str.c_str(), str.length());
-		if ((long unsigned int) bytesWritten != str.length() && (!supressRepeatedWarning ||  warningCounter<1)) {
+		ss << yData[i];
+
+		if(xData != nullptr)
+			ss << ";" << xData[i];
+
+		ss << std::endl;
+
+		auto str = ss.str();
+		auto bytesWritten =  write(socketFd, str.c_str(), str.length());
+		if ((long unsigned int) bytesWritten != str.length() && (!supressRepeatedWarning || warningCounter <1 )) {
 			warning("Could not send all content to socket %s", socketName.c_str());
 			warningCounter++;
 		}
diff --git a/lib/hooks/dft.cpp b/lib/hooks/dft.cpp
index 666368b78..b080eafc9 100644
--- a/lib/hooks/dft.cpp
+++ b/lib/hooks/dft.cpp
@@ -137,6 +137,7 @@ public:
 		signal_list_clear(&signals);
 
 		/* Initialize sample memory */
+		smpMemory.clear();
 		for (unsigned i = 0; i < signalIndex.size(); i++) {
 			struct signal *freqSig;
 			struct signal *amplSig;
@@ -166,6 +167,7 @@ public:
 		freqCount = ceil((endFreqency - startFreqency) / frequencyResolution) + 1;
 
 		/* Initialize matrix of dft coeffients */
+		dftMatrix.clear();
 		for (unsigned i = 0; i < freqCount; i++)
 			dftMatrix.emplace_back(windowSize * windowMultiplier, 0.0);