diff --git a/libs/client_server/piclientserver_server.cpp b/libs/client_server/piclientserver_server.cpp
index edfd2083..aaea5d21 100644
--- a/libs/client_server/piclientserver_server.cpp
+++ b/libs/client_server/piclientserver_server.cpp
@@ -37,6 +37,7 @@ PIClientServer::Server::Server() {
 		auto sc = client_factory();
 		if (!sc) {
 			piCout << "ClientFactory returns nullptr!"_tr("PIClientServer");
+			delete c;
 			return;
 		}
 		sc->createForServer(this, c);
diff --git a/libs/main/core/piwaitevent_p.cpp b/libs/main/core/piwaitevent_p.cpp
index 47983a5d..36ec80bc 100644
--- a/libs/main/core/piwaitevent_p.cpp
+++ b/libs/main/core/piwaitevent_p.cpp
@@ -65,9 +65,9 @@ void PIWaitEvent::destroy() {
 	}
 #else
 	for (int i = 0; i < 2; ++i) {
-		if (pipe_fd[i] != 0) {
+		if (pipe_fd[i] != -1) {
 			::close(pipe_fd[i]);
-			pipe_fd[i] = 0;
+			pipe_fd[i] = -1;
 		}
 	}
 #endif
@@ -140,7 +140,7 @@ bool PIWaitEvent::isCreate() const {
 #ifdef WINDOWS
 	return event;
 #else
-	return pipe_fd[ReadEnd] != 0;
+	return pipe_fd[ReadEnd] != -1;
 #endif
 }
 
diff --git a/libs/main/core/piwaitevent_p.h b/libs/main/core/piwaitevent_p.h
index 9814d449..1af19ac1 100644
--- a/libs/main/core/piwaitevent_p.h
+++ b/libs/main/core/piwaitevent_p.h
@@ -55,7 +55,7 @@ private:
 #ifdef WINDOWS
 	void * event = nullptr;
 #else
-	int pipe_fd[2] = {0, 0};
+	int pipe_fd[2] = {-1, -1};
 	fd_set fds[3];
 	enum {
 		ReadEnd  = 0,
diff --git a/libs/main/io_devices/pican.cpp b/libs/main/io_devices/pican.cpp
index 2d6fe04e..6d1e2295 100644
--- a/libs/main/io_devices/pican.cpp
+++ b/libs/main/io_devices/pican.cpp
@@ -24,6 +24,7 @@
 #  define PIP_CAN
 #endif
 #ifdef PIP_CAN
+#  include <fcntl.h>
 #  include <linux/can.h>
 #  include <linux/can/raw.h>
 #  include <net/if.h>
@@ -49,7 +50,7 @@ PICAN::PICAN(const PIString & path, PIIODevice::DeviceMode mode): PIIODevice(pat
 	setThreadedReadBufferSize(256);
 	setPath(path);
 	can_id = 0;
-	sock   = 0;
+	sock   = -1;
 	PRIVATE->event.create();
 }
 
@@ -67,19 +68,25 @@ bool PICAN::openDevice() {
 	sock = socket(PF_CAN, SOCK_RAW, CAN_RAW);
 	if (sock < 0) {
 		piCoutObj << "Error! while opening socket";
+		sock = -1;
 		return false;
 	}
+	fcntl(sock, F_SETFL, fcntl(sock, F_GETFL) | O_NONBLOCK);
 	ifreq ifr;
 	strcpy(ifr.ifr_name, path().dataAscii());
 	piCout << "PICAN try to get interface index...";
 	if (ioctl(sock, SIOCGIFINDEX, &ifr) < 0) {
 		piCoutObj << "Error! while determin the interface ioctl";
+		::close(sock);
+		sock = -1;
 		return false;
 	}
 	struct timeval tv;
 	tv.tv_sec  = 1;
 	tv.tv_usec = 0;
-	setsockopt(sock, SOL_SOCKET, SO_RCVTIMEO, (const char *)&tv, sizeof tv);
+	if (setsockopt(sock, SOL_SOCKET, SO_RCVTIMEO, (const char *)&tv, sizeof tv) < 0) {
+		piCoutObj << "Error! while setting socket receive timeout";
+	}
 	// bind socket to all CAN interface
 	sockaddr_can addr;
 	addr.can_family  = AF_CAN;
@@ -87,6 +94,8 @@ bool PICAN::openDevice() {
 	piCout << "PICAN try to bind socket to interface" << ifr.ifr_ifindex;
 	if (bind(sock, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
 		piCoutObj << "Error! while binding socket";
+		::close(sock);
+		sock = -1;
 		return false;
 	}
 	piCout << "PICAN Open OK!";
@@ -101,7 +110,11 @@ bool PICAN::openDevice() {
 bool PICAN::closeDevice() {
 #ifdef PIP_CAN
 	interrupt();
-	if (sock > 0) ::close(sock);
+	if (sock != -1) {
+		::shutdown(sock, SHUT_RDWR);
+		::close(sock);
+		sock = -1;
+	}
 #endif
 	return true;
 }
@@ -109,6 +122,7 @@ bool PICAN::closeDevice() {
 
 ssize_t PICAN::readDevice(void * read_to, ssize_t max_size) {
 #ifdef PIP_CAN
+	if (sock == -1) return -1;
 	// piCout << "PICAN read";
 	can_frame frame;
 	ssize_t ret = 0;
@@ -127,6 +141,7 @@ ssize_t PICAN::readDevice(void * read_to, ssize_t max_size) {
 
 ssize_t PICAN::writeDevice(const void * data, ssize_t max_size) {
 #ifdef PIP_CAN
+	if (sock == -1) return -1;
 	// piCout << "PICAN write" << can_id << max_size;
 	if (max_size > 8) {
 		piCoutObj << "Can't send CAN frame bigger than 8 bytes (requested " << max_size << ")!";
diff --git a/libs/main/io_devices/pican.h b/libs/main/io_devices/pican.h
index 93bef921..37938818 100644
--- a/libs/main/io_devices/pican.h
+++ b/libs/main/io_devices/pican.h
@@ -73,7 +73,7 @@ protected:
 
 private:
 	PRIVATE_DECLARATION(PIP_EXPORT)
-	int sock;
+	int sock = -1;
 	int can_id, readed_id;
 };
 
diff --git a/libs/main/io_devices/piethernet.cpp b/libs/main/io_devices/piethernet.cpp
index ad4a08b3..a1245cc1 100644
--- a/libs/main/io_devices/piethernet.cpp
+++ b/libs/main/io_devices/piethernet.cpp
@@ -383,7 +383,7 @@ void PIEthernet::applyBuffers() {
 
 void PIEthernet::applyTimeout(int fd, int opt, PISystemTime tm) {
 	if (fd == 0) return;
-	// piCoutObj << "setReadIsBlocking" << yes;
+		// piCoutObj << "setReadIsBlocking" << yes;
 #ifdef WINDOWS
 	DWORD _tm = tm.toMilliseconds();
 #else
@@ -1234,7 +1234,7 @@ PIEthernet::InterfaceList PIEthernet::interfaces() {
 #	  ifdef QNX
 #		ifndef BLACKBERRY
 			int fd = ::open((PIString("/dev/io-net/") + ci.name).dataAscii(), O_RDONLY);
-			if (fd != 0) {
+			if (fd >= 0) {
 				nic_config_t nic;
 				devctl(fd, DCMD_IO_NET_GET_CONFIG, &nic, sizeof(nic), 0);
 				::close(fd);
diff --git a/libs/main/io_devices/piiobytearray.cpp b/libs/main/io_devices/piiobytearray.cpp
index 3b6e8374..699bd1e9 100644
--- a/libs/main/io_devices/piiobytearray.cpp
+++ b/libs/main/io_devices/piiobytearray.cpp
@@ -62,8 +62,7 @@ ssize_t PIIOByteArray::readDevice(void * read_to, ssize_t size) {
 	if (ret <= 0) return -1;
 	memcpy(read_to, data_->data(pos), ret);
 	// piCout << "readed" << ret;
-	pos += size;
-	if (pos > data_->size_s()) pos = data_->size_s();
+	pos += ret;
 	return ret;
 }
 
diff --git a/libs/main/io_devices/pipeer.cpp b/libs/main/io_devices/pipeer.cpp
index c121dfea..0cf8bd6a 100644
--- a/libs/main/io_devices/pipeer.cpp
+++ b/libs/main/io_devices/pipeer.cpp
@@ -623,7 +623,10 @@ bool PIPeer::dataRead(const uchar * readed, ssize_t size) {
 			return true;
 		}
 		cnt++;
-		if (cnt > _PIPEER_MSG_TTL || from == dp->name) return true;
+		if (cnt > _PIPEER_MSG_TTL || from == dp->name) {
+			eth_mutex.unlock();
+			return true;
+		}
 		sba << type << from << to << cnt << pba;
 		// piCout << "translate packet" << from << "->" << to << ", ttl =" << cnt;
 		sendToNeighbour(dp, sba);
diff --git a/libs/main/io_devices/piserial.cpp b/libs/main/io_devices/piserial.cpp
index 9859ef68..401d5dfc 100644
--- a/libs/main/io_devices/piserial.cpp
+++ b/libs/main/io_devices/piserial.cpp
@@ -513,7 +513,10 @@ bool PISerial::read(void * data, int size, double timeout_ms) {
 		all     = readDevice(data, 1);
 		while (all < size) {
 			ret = readDevice(&((uchar *)data)[all], size - all);
-			if (ret > 0) all += ret;
+			if (ret > 0)
+				all += ret;
+			else
+				break;
 		}
 		setOption(BlockingRead, br);
 		received(data, all);
@@ -1235,8 +1238,8 @@ PIVector<PISerial::DeviceInfo> PISerial::availableDevicesInfo(bool test) {
 	for (const auto & e: de) { // TODO changes in FileInfo
 		for (const auto & p: prefixes) {
 			if (e.name().startsWith(p)) {
-				di      = DeviceInfo();
-				di.path = e.path;
+				di          = DeviceInfo();
+				di.path     = e.path;
 #	ifdef LINUX
 				ssize_t lsz = readlink(("/sys/class/tty/" + e.name()).dataAscii(), linkbuf, 1024);
 				if (lsz > 0) {
diff --git a/libs/main/io_utils/pifiletransfer.cpp b/libs/main/io_utils/pifiletransfer.cpp
index 7389a769..acdeac73 100644
--- a/libs/main/io_utils/pifiletransfer.cpp
+++ b/libs/main/io_utils/pifiletransfer.cpp
@@ -131,6 +131,12 @@ bool PIFileTransfer::sendFiles(const PIVector<PFTFileInfo> & files) {
 
 void PIFileTransfer::processFile(int id, ullong start, PIByteArray & data) {
 	// piCout << "processFile" << id << files_.size();
+	if (id <= 0 || id > files_.size_s()) {
+		cur_file_string = "Error: Invalid file id " + PIString::fromNumber(id);
+		piCoutObj << cur_file_string;
+		stopReceive();
+		return;
+	}
 	PFTFileInfo fi  = files_[id - 1];
 	bytes_file_all  = fi.size;
 	bytes_file_cur  = start;
diff --git a/libs/main/system/piprocess.cpp b/libs/main/system/piprocess.cpp
index ffa6a871..115b9a69 100644
--- a/libs/main/system/piprocess.cpp
+++ b/libs/main/system/piprocess.cpp
@@ -319,6 +319,13 @@ void PIProcess::startProc(bool detached) {
 	auto largs = convertToCharArrays(args);
 	auto lenv  = convertToCharArrays(env);
 	int pid_   = fork();
+	if (pid_ < 0) {
+		piCoutObj << "\"fork\" error: " << errorString();
+		PRIVATE->closeAllPipes();
+		delete[] largs;
+		delete[] lenv;
+		return;
+	}
 	if (!detached) PRIVATE->pid = pid_;
 	if (pid_ == 0) {
 		if (!wd.isEmpty()) {
diff --git a/libs/main/text/pistring.cpp b/libs/main/text/pistring.cpp
index db3b9da8..65bf8035 100644
--- a/libs/main/text/pistring.cpp
+++ b/libs/main/text/pistring.cpp
@@ -671,7 +671,7 @@ PIString & PIString::operator+=(const PIConstChars & str) {
 	if (!str.isEmpty()) {
 		size_t os = d.size();
 		d.enlarge(str.size());
-		for (size_t l = 0; l < d.size(); ++l) {
+		for (size_t l = 0; l < str.size(); ++l) {
 			d[os + l] = str[l];
 		}
 	}
@@ -1763,7 +1763,7 @@ PIString PIString::toLowerCase() const {
 
 
 char PIString::toChar() const {
-	char v;
+	char v = 0;
 	sscanf(dataAscii(), "%c", &v);
 	return v;
 }
diff --git a/libs/mqtt_client/pimqttclient.cpp b/libs/mqtt_client/pimqttclient.cpp
index 60ffb958..133639e5 100644
--- a/libs/mqtt_client/pimqttclient.cpp
+++ b/libs/mqtt_client/pimqttclient.cpp
@@ -60,7 +60,7 @@ STATIC_INITIALIZER_END
 
 PRIVATE_DEFINITION_START(PIMQTT::Client)
 	MQTTClient client = nullptr;
-	bool connected    = false;
+	std::atomic<bool> connected{false};
 
 	PIProtectedVariable<EndpointsStorage> endpoints;