Deze routine word gebruikt in de Aquacontroller.
Haalt ongeveer 14kB/s. Maar kan wel 1.3MB grote bestanden aan.

void fileSend(String fileName) {
 SPIFFS.begin();
 File thisFile = SPIFFS.open(fileName, "r");
 if (!thisFile) {
   webClient.println("HTTP/1.1 404 Not found\r\n");
   webClient.println("ERROR 404 - '" + fileName + "' was not found.");
   return;
 }
 //check the file's extention and tailor the header for that
 String httpHeader;
 if ( fileName.substring( fileName.length() - 4 ) == ".css" ) {
   httpHeader = "HTTP/1.1 200 \r\nContent-Type: text/css\r\n";
 } 
 else {
   httpHeader = "HTTP/1.1 200 \r\nContent-Type: text/html\r\n";
 }
 httpHeader += "Content-Length: " + (String)thisFile.size() + "\r\n" ;
 webClient.println(httpHeader);

 int bufferSize = 512;
 char rwBuffer[bufferSize];
 while ( thisFile.available() > bufferSize ) {
   for ( int bufferPos = 0; bufferPos < bufferSize; bufferPos++ ) {
     rwBuffer[bufferPos] = thisFile.read();
   }
   webClient.write(rwBuffer, bufferSize);
 }
 //send last chunk
 int leftOver = thisFile.available();
 for ( int bufferPos = 0; bufferPos < leftOver; bufferPos++ ) {
   rwBuffer[bufferPos] = thisFile.read();
 }
 webClient.write(rwBuffer, leftOver);
 thisFile.close();
}