diff --git a/src/lib/ebus/device.cpp b/src/lib/ebus/device.cpp
index 41b14410..ce324c75 100755
--- a/src/lib/ebus/device.cpp
+++ b/src/lib/ebus/device.cpp
@@ -57,9 +57,30 @@ namespace ebusd {
 #define ENH_STARTED ((symbol_t)0x02)
 #define ENH_FAILED ((symbol_t)0x82)
 
+/**
+ * Construct a new instance.
+ * @param name the device name (e.g. "/dev/ttyUSB0" for serial, "127.0.0.1:1234" for network).
+ * @param address the socket address of the device.
+ * @param readOnly whether to allow read access to the device only.
+ * @param initialSend whether to send an initial @a ESC symbol in @a open().
+ * @param udp true for UDP, false to TCP.
+ * @param enhancedProto whether the device supports the ebusd enhanced protocol.
+ */
+Device::Device(const char* name, bool checkDevice, bool readOnly, bool initialSend, bool enhancedProto)
+  : m_name(name), m_checkDevice(checkDevice), m_readOnly(readOnly), m_initialSend(initialSend),
+    m_enhancedProto(enhancedProto), m_fd(-1), m_listener(nullptr), m_arbitrationMaster(SYN),
+    m_arbitrationCheck(false), m_bufSize(((MAX_LEN+1+3)/4)*4), m_bufLen(0), m_bufPos(0) {
+  m_buffer = reinterpret_cast<symbol_t*>(malloc(m_bufSize));
+  if (!m_buffer) {
+    m_bufSize = 0;
+  }
+}
 
 Device::~Device() {
   close();
+  if (m_buffer) {
+    free(m_buffer);
+  }
 }
 
 Device* Device::create(const char* name, bool checkDevice, bool readOnly, bool initialSend) {
@@ -72,6 +93,10 @@ Device* Device::create(const char* name, bool checkDevice, bool readOnly, bool i
     if (portpos >= addrpos+3 && strncmp(addrpos, "enh", 3) == 0) {
       enhanced = true;
       addrpos += 3;
+      if (portpos == addrpos) {
+        addrpos++;
+        portpos = strchr(addrpos, ':');
+      }
     }
     if (portpos == addrpos+3 && (strncmp(addrpos, "tcp", 3) == 0 || (udp=(strncmp(addrpos, "udp", 3) == 0)))) {
       addrpos += 4;
@@ -106,11 +131,17 @@ Device* Device::create(const char* name, bool checkDevice, bool readOnly, bool i
   return new SerialDevice(name, checkDevice, readOnly, initialSend);
 }
 
+result_t Device::open() {
+  close();
+  return m_bufSize == 0 ? RESULT_ERR_DEVICE : RESULT_OK;
+}
+
 void Device::close() {
   if (m_fd != -1) {
     ::close(m_fd);
     m_fd = -1;
   }
+  m_bufLen = 0;  // flush read buffer
 }
 
 bool Device::isValid() {
@@ -140,7 +171,8 @@ result_t Device::recv(unsigned int timeout, symbol_t* value, ArbitrationState* a
   if (!isValid()) {
     return RESULT_ERR_DEVICE;
   }
-  if (!available() && timeout > 0) {
+  bool isAvailable = available();
+  if (!isAvailable && timeout > 0) {
     int ret;
     struct timespec tdiff;
 
@@ -185,18 +217,18 @@ result_t Device::recv(unsigned int timeout, symbol_t* value, ArbitrationState* a
     }
   }
 
+  ArbitrationState prevState = *arbitrationState;
   // directly read byte from device
-  if (!read(value, m_enhancedProto ? arbitrationState : nullptr)) {
+  if (!read(value, isAvailable, arbitrationState)) {
     close();
     return RESULT_ERR_DEVICE;
   }
-  ArbitrationState prevState = m_enhancedProto && arbitrationState ? *arbitrationState : as_none;
-  if (*value != SYN || m_arbitrationMaster == SYN || m_enhancedProto) {
+  if (m_enhancedProto || *value != SYN || m_arbitrationMaster == SYN) {
     if (m_listener != nullptr) {
       m_listener->notifyDeviceData(*value, true);
     }
     if (m_enhancedProto) {
-      if (arbitrationState && *arbitrationState != prevState) {
+      if (*arbitrationState != prevState) {
         m_arbitrationMaster = SYN;
         m_arbitrationCheck = false;
       }
@@ -236,32 +268,116 @@ result_t Device::startArbitration(symbol_t masterAddress) {
   if (m_readOnly) {
     return RESULT_ERR_SEND;
   }
-  m_arbitrationCheck = false;
   m_arbitrationMaster = masterAddress;
-  if (m_enhancedProto) {
+  m_arbitrationCheck = false;
+  if (m_enhancedProto && masterAddress != SYN) {
     if (!write(masterAddress, true)) {
       m_arbitrationMaster = SYN;
-      m_arbitrationCheck = false;
       return RESULT_ERR_SEND;
     }
     m_arbitrationCheck = true;
-    return RESULT_OK;
   }
   return RESULT_OK;
 }
 
 bool Device::write(symbol_t value, bool startArbitration) {
+  if (m_enhancedProto) {
+    symbol_t buf[2] = {startArbitration ? ENH_START : ENH_SEND, value};
+    return ::write(m_fd, buf, 2) == 2;
+  }
   return ::write(m_fd, &value, 1) == 1;
 }
 
-bool Device::read(symbol_t* value, ArbitrationState* arbitrationState) {
-  return ::read(m_fd, value, 1) == 1;
+bool Device::available() {
+  if (m_bufLen <= 0) {
+    return false;
+  }
+  if (!m_enhancedProto) {
+    return true;
+  }
+  // peek into the received enhanced proto bytes to determine symbol availability
+  for (size_t pos = 0; pos < m_bufLen; pos++) {
+    symbol_t ch = m_buffer[(pos+m_bufPos)%m_bufSize];
+    if (ch == ENH_RECEIVED) {
+      return pos+1 < m_bufLen;
+    }
+  }
+  return false;
+}
+
+bool Device::read(symbol_t* value, bool isAvailable, ArbitrationState* arbitrationState) {
+  if (!isAvailable) {
+    if (m_bufLen > 0 && m_bufPos != 0) {
+      if (m_bufLen > m_bufSize / 2) {
+        m_bufLen = 0; // TODO report error
+      } else {
+        size_t tail;
+        if (m_bufPos+m_bufLen > m_bufSize) {
+          // move wrapped tail away
+          tail = (m_bufPos+m_bufLen) % m_bufSize;
+          size_t head = m_bufLen-tail;
+          memmove(m_buffer+head, m_buffer, tail);
+        } else {
+          tail = 0;
+        }
+        // move head to first position
+        memmove(m_buffer, m_buffer + m_bufPos, m_bufLen - tail);
+      }
+    }
+    m_bufPos = 0;
+    // fill up the buffer
+    ssize_t size = ::read(m_fd, m_buffer + m_bufLen, m_bufSize - m_bufLen);
+    if (size <= 0) {
+      return false;
+    }
+    m_bufLen += size;
+  }
+  if (!available()) {
+    return false;
+  }
+  if (!m_enhancedProto) {
+    *value = m_buffer[m_bufPos];
+    m_bufPos = (m_bufPos+1)%m_bufSize;
+    m_bufLen--;
+    return true;
+  }
+  while (m_bufLen > 0) {
+    symbol_t ch = m_buffer[m_bufPos];
+    m_bufPos = (m_bufPos+1)%m_bufSize;
+    m_bufLen--;
+    switch (ch) {
+      case ENH_STARTED:
+        *arbitrationState = as_won;
+        m_arbitrationMaster = SYN;
+        break;
+      case ENH_FAILED:
+        *arbitrationState = as_error;
+        m_arbitrationMaster = SYN;
+        break;
+      case ENH_RECEIVED:
+        if (m_bufLen <= 0) {
+          return false;
+        }
+        *value = m_buffer[m_bufPos];
+        m_bufPos = (m_bufPos+1)%m_bufSize;
+        m_bufLen--;
+        return true;
+      case ENH_RESETTED: // TODO
+        *arbitrationState = as_error;
+        break;
+      default:
+        // TODO proto error
+        return false;
+    }
+  }
+  return false;
 }
 
 
 result_t SerialDevice::open() {
-  if (m_fd != -1) {
-    close();
+  result_t result = Device::open();
+  if (result != RESULT_OK) {
+    return result;
   }
   struct termios newSettings;
 
@@ -339,8 +455,9 @@ void SerialDevice::checkDevice() {
 
 
 result_t NetworkDevice::open() {
-  if (m_fd != -1) {
-    close();
+  result_t result = Device::open();
+  if (result != RESULT_OK) {
+    return result;
   }
   m_fd = socket(AF_INET, m_udp ? SOCK_DGRAM : SOCK_STREAM, 0);
   if (m_fd < 0) {
@@ -376,13 +493,6 @@ result_t NetworkDevice::open() {
       break;
     }
   }
-  if (m_bufSize == 0) {
-    m_bufSize = MAX_LEN+1;
-    m_buffer = reinterpret_cast<symbol_t*>(malloc(m_bufSize));
-    if (!m_buffer) {
-      m_bufSize = 0;
-    }
-  }
   m_bufLen = 0;
   if (m_initialSend && !write(ESC)) {
     return RESULT_ERR_SEND;
@@ -390,11 +500,6 @@ result_t NetworkDevice::open() {
   return RESULT_OK;
 }
 
-void NetworkDevice::close() {
-  m_bufLen = 0;  // flush read buffer
-  Device::close();
-}
-
 void NetworkDevice::checkDevice() {
   int cnt;
   if (ioctl(m_fd, FIONREAD, &cnt) < 0) {
@@ -402,74 +507,4 @@ void NetworkDevice::checkDevice() {
   }
 }
 
-bool NetworkDevice::available() {
-  return m_buffer && m_bufLen > 0;
-}
-
-bool NetworkDevice::write(symbol_t value, bool startArbitration) {
-  m_bufLen = 0;  // flush read buffer
-  if (m_bufSize > 0 && m_enhancedProto) {
-    m_buffer[0] = startArbitration ? ENH_START : ENH_SEND;
-    m_buffer[1] = value;
-    return ::write(m_fd, m_buffer, 2) == 2;
-  }
-  return Device::write(value);
-}
-
-bool NetworkDevice::read(symbol_t* value, ArbitrationState* arbitrationState) {
-  if (available()) {
-    *value = m_buffer[m_bufPos];
-    m_bufPos = (m_bufPos+1)%m_bufSize;
-    m_bufLen--;
-    return true;
-  }
-  if (m_bufSize > 0) {
-    ssize_t size = ::read(m_fd, m_buffer, m_bufSize);
-    if (size <= 0) {
-      return false;
-    }
-    if (m_enhancedProto) {
-      symbol_t* buf = m_buffer;
-      m_bufPos = 0;
-      m_bufLen = 0;
-      while (size > 0) {
-        buf++;
-        size--;
-        switch (*buf) {
-          case ENH_STARTED:
-            if (arbitrationState) {
-              *arbitrationState = as_won;
-            }
-            break;
-          case ENH_FAILED:
-            if (arbitrationState) {
-              *arbitrationState = as_error;
-            }
-            break;
-          case ENH_RECEIVED:
-            m_buffer[m_bufPos++] = *buf;
-            m_bufLen++;
-            break;
-          case ENH_RESETTED: // TODO
-            break;
-          default:
-            return false;
-        }
-      }
-      if (m_bufLen > 0) {
-        *value = m_buffer[0];
-        m_bufPos = 1;
-        m_bufLen--;
-        return true;
-      }
-      return false;
-    }
-    *value = m_buffer[0];
-    m_bufPos = 1;
-    m_bufLen = size-1;
-    return true;
-  }
-  return Device::read(value, arbitrationState);
-}
-
 }  // namespace ebusd
diff --git a/src/lib/ebus/device.h b/src/lib/ebus/device.h
index 92768e33..84576291 100755
--- a/src/lib/ebus/device.h
+++ b/src/lib/ebus/device.h
@@ -81,10 +81,7 @@ class Device {
    * @param initialSend whether to send an initial @a ESC symbol in @a open().
    * @param enhancedProto whether the device supports the ebusd enhanced protocol.
    */
-  Device(const char* name, bool checkDevice, bool readOnly, bool initialSend, bool enhancedProto=false)
-    : m_name(name), m_checkDevice(checkDevice), m_readOnly(readOnly), m_initialSend(initialSend),
-      m_enhancedProto(enhancedProto), m_fd(-1), m_listener(nullptr), m_arbitrationMaster(SYN),
-      m_arbitrationCheck(false) {}
+  Device(const char* name, bool checkDevice, bool readOnly, bool initialSend, bool enhancedProto=false);
 
   /**
    * Destructor.
@@ -113,7 +110,7 @@ class Device {
    * Open the file descriptor.
    * @return the @a result_t code.
    */
-  virtual result_t open() = 0;  // abstract
+  virtual result_t open();
 
   /**
    * Close the file descriptor if opened.
@@ -178,12 +175,6 @@ class Device {
    */
   virtual void checkDevice() = 0;  // abstract
 
-  /**
-   * Check whether a byte is available immediately (without waiting).
-   * @return true when a a byte is available immediately.
-   */
-  virtual bool available() { return false; }
-
   /**
    * Write a single byte.
    * @param value the byte value to write.
@@ -191,12 +182,20 @@ class Device {
    */
   virtual bool write(symbol_t value, bool startArbitration=false);
 
+  /**
+   * Check whether a symbol is available for reading immediately (without waiting).
+   * @return true when a symbol is available for reading immediately.
+   */
+  virtual bool available();
+
   /**
    * Read a single byte.
    * @param value the reference in which the read byte value is stored.
+   * @param isAvailable the result of the immediately preceding call to @a available().
+   * @param arbitrationState the variable in which to store the received arbitration state (mandatory for enhanced proto).
    * @return true on success, false on error.
    */
-  virtual bool read(symbol_t* value, ArbitrationState* arbitrationState=nullptr);
+  virtual bool read(symbol_t* value, bool isAvailable, ArbitrationState* arbitrationState=nullptr);
 
   /** the device name (e.g. "/dev/ttyUSB0" for serial, "127.0.0.1:1234" for network). */
   const char* m_name;
@@ -219,15 +218,28 @@ class Device {
 
  private:
   /** the @a DeviceListener, or nullptr. */
-  DeviceListener* m_listener;
+public: DeviceListener* m_listener;
 
   /** the arbitration master address to send when in arbitration, or @a SYN. */
   symbol_t m_arbitrationMaster;
 
   /** true when in arbitration and the next received symbol needs to be checked against the sent master address. */
   bool m_arbitrationCheck;
+
+  /** the read buffer. */
+  symbol_t* m_buffer;
+
+  /** the read buffer size (multiple of 4). */
+  size_t m_bufSize;
+
+  /** the read buffer fill length. */
+  size_t m_bufLen;
+
+  /** the read buffer read position. */
+  size_t m_bufPos;
 };
 
+
 /**
  * The @a Device for directly connected serial interfaces (tty).
  */
@@ -276,17 +288,12 @@ class NetworkDevice : public Device {
    */
   NetworkDevice(const char* name, const struct sockaddr_in& address, bool readOnly, bool initialSend,
     bool udp, bool enhancedProto=false)
-    : Device(name, true, readOnly, initialSend, enhancedProto), m_address(address), m_udp(udp),
-      m_buffer(nullptr), m_bufSize(0), m_bufLen(0), m_bufPos(0) {}
+    : Device(name, true, readOnly, initialSend, enhancedProto), m_address(address), m_udp(udp) {}
 
   /**
    * Destructor.
    */
-  virtual ~NetworkDevice() {
-    if (m_buffer) {
-      free(m_buffer);
-    }
-  }
+  ~NetworkDevice() override {}
 
   // @copydoc
   unsigned int getLatency() const override { return 10000; }
@@ -294,22 +301,11 @@ class NetworkDevice : public Device {
   // @copydoc
   result_t open() override;
 
-  // @copydoc
-  void close() override;
 
  protected:
   // @copydoc
   void checkDevice() override;
 
-  // @copydoc
-  bool available() override;
-
-  // @copydoc
-  bool write(symbol_t value, bool startArbitration=false) override;
-
-  // @copydoc
-  bool read(symbol_t* value, ArbitrationState* arbitrationState=nullptr) override;
-
 
  private:
   /** the socket address of the device. */
@@ -317,18 +313,6 @@ class NetworkDevice : public Device {
 
   /** true for UDP, false to TCP. */
   const bool m_udp;
-
-  /** the buffer memory, or nullptr. */
-  symbol_t* m_buffer;
-
-  /** the buffer size. */
-  size_t m_bufSize;
-
-  /** the buffer fill length. */
-  size_t m_bufLen;
-
-  /** the buffer read position. */
-  size_t m_bufPos;
 };
 
 }  // namespace ebusd