Host stream write buffer for message oriented transmits

utility/EthernetClientStream.h

@@ -31,6 +31,17 @@
 #define HOST_CONNECTION_DISCONNECTED 0
 #define HOST_CONNECTION_CONNECTED    1
 
+// If defined and set to a value higher than 1 all single bytes writes
+// will be buffered until one of the following conditions is met:
+// 1) write buffer full
+// 2) any call to read(), available(), maintain(), peek() or flush()
+// By combining the buffered bytes into a single TCP frame this feature will significantly 
+// reduce the network and receiver load by the factor 1/(1/20 + 1/bufferedSize).
+// Buffer sizes up to 80 have been tested successfully. Note that higher buffer values 
+// may cause slight delays between an event and the network transmission.
+#define WRITE_BUFFER_SIZE 40
+
+
 extern "C" {
   // callback function types
   typedef void (*hostConnectionCallbackFunction)(byte);
@@ -56,6 +67,10 @@ class EthernetClientStream : public Stream
     uint16_t port;
     bool connected;
     uint32_t time_connect;
+#ifdef WRITE_BUFFER_SIZE
+    uint8_t writeBuffer[WRITE_BUFFER_SIZE];
+    uint8_t writeBufferLength;
+#endif    
     hostConnectionCallbackFunction currentHostConnectionCallback;
     bool maintain();
     void stop();
@@ -73,8 +88,11 @@ EthernetClientStream::EthernetClientStream(Client &client, IPAddress localip, IP
     ip(ip),
     host(host),
     port(port),
-    connected(false)
-    , currentHostConnectionCallback(nullptr)
+    connected(false),
+#ifdef WRITE_BUFFER_SIZE
+    writeBufferLength(0),
+#endif
+    currentHostConnectionCallback(nullptr)
 {
 }
 
@@ -105,7 +123,20 @@ void EthernetClientStream::flush()
 size_t
 EthernetClientStream::write(uint8_t c)
 {
+#ifdef WRITE_BUFFER_SIZE
+  if (connected) {
+    // buffer new byte and send buffer when full
+    writeBuffer[writeBufferLength++] = c;
+    if (writeBufferLength >= WRITE_BUFFER_SIZE) {
+      return maintain()? 1 : 0;
+    }
+    return 1;
+  } else {
+    return 0;
+  }
+#else
   return maintain() ? client.write(c) : 0;
+#endif
 }
 
 void
@@ -128,6 +159,9 @@ EthernetClientStream::stop()
     (*currentHostConnectionCallback)(HOST_CONNECTION_DISCONNECTED);
   }
   connected = false;
+#ifdef WRITE_BUFFER_SIZE
+  writeBufferLength = 0;
+#endif
   time_connect = millis();
 }
 
@@ -140,8 +174,16 @@ EthernetClientStream::attach(hostConnectionCallbackFunction newFunction)
 bool
 EthernetClientStream::maintain()
 {
-  if (client && client.connected())
+  if (client && client.connected()) {
+#ifdef WRITE_BUFFER_SIZE
+    // send buffered bytes
+    if (writeBufferLength) {
+      client.write(writeBuffer, writeBufferLength);
+      writeBufferLength = 0;
+    }
+#endif
     return true;
+  }
 
   if (connected) {
     stop();
@@ -153,6 +195,9 @@ EthernetClientStream::maintain()
       time_connect = millis();
       DEBUG_PRINTLN("Connection failed. Attempting to reconnect...");
     } else {
+#ifdef WRITE_BUFFER_SIZE
+      writeBufferLength = 0;
+#endif
       DEBUG_PRINTLN("Connected");
       if (currentHostConnectionCallback)
       {

utility/EthernetServerStream.h

@@ -10,7 +10,7 @@
 
   See file LICENSE.txt for further informations on licensing terms.
 
-  Last updated July 10th, 2017
+  Last updated March 21st 2020
  */
 
 #ifndef ETHERNETSERVERSTREAM_H
@@ -23,6 +23,17 @@
 //#define SERIAL_DEBUG
 #include "firmataDebug.h"
 
+// If defined and set to a value higher than 1 all single bytes writes
+// will be buffered until one of the following conditions is met:
+// 1) write buffer full
+// 2) any call to read(), available(), maintain(), peek() or flush()
+// By combining the buffered bytes into a single TCP frame this feature will significantly 
+// reduce the network and receiver load by the factor 1/(1/20 + 1/bufferedSize).
+// Buffer sizes up to 80 have been tested successfully. Note that higher buffer values 
+// may cause slight delays between an event and the network transmission.
+#define WRITE_BUFFER_SIZE 40
+
+
 class EthernetServerStream : public Stream
 {
   public:
@@ -39,6 +50,10 @@ class EthernetServerStream : public Stream
     IPAddress localip;
     uint16_t port;
     bool connected;
+#ifdef WRITE_BUFFER_SIZE
+    uint8_t writeBuffer[WRITE_BUFFER_SIZE];
+    uint8_t writeBufferLength;
+#endif    
     bool maintain();
     void stop();
 
@@ -58,21 +73,37 @@ EthernetServerStream::EthernetServerStream(IPAddress localip, uint16_t port)
   : localip(localip),
     port(port),
     connected(false)
+#ifdef WRITE_BUFFER_SIZE
+    , writeBufferLength(0)
+#endif    
 {
 }
 
 bool EthernetServerStream::connect_client()
   {
     if ( connected )
     {
-      if ( client && client.connected() ) return true;
+      if ( client && client.connected() )
+      {
+#ifdef WRITE_BUFFER_SIZE
+        // send buffered bytes
+        if (writeBufferLength) {
+          client.write(writeBuffer, writeBufferLength);
+          writeBufferLength = 0;
+        }
+#endif  
+        return true;
+      }
       stop();
     }
 
     EthernetClient newClient = server.available();
     if ( !newClient ) return false;
     client = newClient;
     connected = true;
+#ifdef WRITE_BUFFER_SIZE
+    writeBufferLength = 0;
+#endif  
     DEBUG_PRINTLN("Connected");
     return true;
   }
@@ -126,6 +157,9 @@ EthernetServerStream::stop()
     client.stop();
   }
   connected = false;
+#ifdef WRITE_BUFFER_SIZE
+  writeBufferLength = 0;
+#endif  
 }
 
 bool

utility/WiFiClientStream.h

@@ -20,7 +20,7 @@
 
   published under the same license.
 
-  Last updated April 23rd, 2016
+  Last updated March 21st, 2020
  */
 
 #ifndef WIFI_CLIENT_STREAM_H
@@ -43,7 +43,17 @@ class WiFiClientStream : public WiFiStream
   {
     if ( _connected )
     {
-      if ( _client && _client.connected() ) return true;
+      if ( _client && _client.connected() )
+      {
+#ifdef WRITE_BUFFER_SIZE
+        // send buffered bytes
+        if (writeBufferLength) {
+          _client.write(writeBuffer, writeBufferLength);
+          writeBufferLength = 0;
+        }
+#endif
+        return true;
+      }
       stop();
     }
 
@@ -58,9 +68,15 @@ class WiFiClientStream : public WiFiStream
         {
           _time_connect = millis();
         }
-        else if ( _currentHostConnectionCallback )
+        else
         {
-          (*_currentHostConnectionCallback)(HOST_CONNECTION_CONNECTED);
+#ifdef WRITE_BUFFER_SIZE
+          writeBufferLength = 0;
+#endif
+          if ( _currentHostConnectionCallback )
+          {
+            (*_currentHostConnectionCallback)(HOST_CONNECTION_CONNECTED);
+          }
         }
       }
     }
@@ -97,6 +113,9 @@ class WiFiClientStream : public WiFiStream
       }
     }
     _connected = false;
+#ifdef WRITE_BUFFER_SIZE
+    writeBufferLength = 0;
+#endif
     _time_connect = millis();
   }
 

utility/WiFiServerStream.h

@@ -42,7 +42,17 @@ class WiFiServerStream : public WiFiStream
   {
     if ( _connected )
     {
-      if ( _client && _client.connected() ) return true;
+      if ( _client && _client.connected() )
+      {
+#ifdef WRITE_BUFFER_SIZE
+        // send buffered bytes
+        if (writeBufferLength) {
+          _client.write(writeBuffer, writeBufferLength);
+          writeBufferLength = 0;
+        }
+#endif
+        return true;
+      }
       stop();
     }
 
@@ -51,6 +61,9 @@ class WiFiServerStream : public WiFiStream
     if ( !newClient ) return false;
     _client = newClient;
     _connected = true;
+#ifdef WRITE_BUFFER_SIZE
+    writeBufferLength = 0;
+#endif
     if ( _currentHostConnectionCallback )
     {
       (*_currentHostConnectionCallback)(HOST_CONNECTION_CONNECTED);
@@ -100,6 +113,9 @@ class WiFiServerStream : public WiFiStream
       }
     }
     _connected = false;
+#ifdef WRITE_BUFFER_SIZE
+    writeBufferLength = 0;
+#endif
   }
 
 };

utility/WiFiStream.h

@@ -15,7 +15,7 @@
 
   See file LICENSE.txt for further informations on licensing terms.
 
-  Last updated April 23rd, 2016
+  Last updated March 21st, 2020
  */
 
 #ifndef WIFI_STREAM_H
@@ -27,6 +27,17 @@
 #define HOST_CONNECTION_DISCONNECTED 0
 #define HOST_CONNECTION_CONNECTED    1
 
+// If defined and set to a value higher than 1 all single bytes writes
+// will be buffered until one of the following conditions is met:
+// 1) write buffer full
+// 2) any call to read(), available(), maintain(), peek() or flush()
+// By combining the buffered bytes into a single TCP frame this feature will significantly
+// reduce the network and receiver load by the factor 1/(1/20 + 1/bufferedSize).
+// Buffer sizes up to 80 have been tested successfully. Note that higher buffer values
+// may cause slight delays between an event and the network transmission.
+#define WRITE_BUFFER_SIZE 40
+
+
 extern "C" {
   // callback function types
   typedef void (*hostConnectionCallbackFunction)(byte);
@@ -38,6 +49,10 @@ class WiFiStream : public Stream
   WiFiClient _client;
   bool _connected = false;
   hostConnectionCallbackFunction _currentHostConnectionCallback;
+#ifdef WRITE_BUFFER_SIZE
+  uint8_t writeBuffer[WRITE_BUFFER_SIZE];
+  uint8_t writeBufferLength;
+#endif
 
   //configuration members
   IPAddress _local_ip;                // DHCP
@@ -58,7 +73,11 @@ class WiFiStream : public Stream
 
 public:
   /** constructor for TCP server */
-  WiFiStream(uint16_t server_port) : _port(server_port) {}
+  WiFiStream(uint16_t server_port) :
+#ifdef WRITE_BUFFER_SIZE
+    writeBufferLength(0),
+#endif
+    _port(server_port) {}
 
   /** constructor for TCP client */
   WiFiStream(IPAddress server_ip, uint16_t server_port) : _remote_ip(server_ip), _port(server_port) {}
@@ -218,7 +237,20 @@ class WiFiStream : public Stream
 
   inline size_t write(uint8_t byte)
   {
+#ifdef WRITE_BUFFER_SIZE
+    if (connect_client()) {
+      // buffer new byte and send buffer when full
+      writeBuffer[writeBufferLength++] = byte;
+      if (writeBufferLength >= WRITE_BUFFER_SIZE) {
+        return maintain()? 1 : 0;
+      }
+      return 1;
+    } else {
+      return 0;
+    }
+#else
     return connect_client() ? _client.write( byte ) : 0;
+#endif
   }
 
 };