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Topic: Upper limit for client.print() string length (Read 6933 times) previous topic - next topic


I have just been writing a program using ESP8266 WifiClient client.print.  And I can verify that the maximum is just under 3000 bytes.  I believe the size stated above (2922) is probably correct.  I wish it was larger and don't yet know why but will investigate.  It does not cause an error to try to print a longer string but it does truncate it so there must be a buffer somewhere that is limiting the size.

It has been found by several people that multiple client.print statements are slow so I build up the string as long as I can before doing the client.print.  Doing that, it is reasonably fast.  Also, using WiFiClient allows me to leave the connection open for more speed.

Previously, I was using ESP8266WebServer and there is a limit there, too.  It is larger.  Something around 8KB and it won't go above that.  I was not able to find how to do multiple
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httpServer.send(200, "text/html" style commands so I converted to the lower level WifiClient library code.  This gives me access to all of the input lines from the browser and I can track browser type, environment and IP address:port.

There is a hierachy here:
ESP8266HTTPUpdateServer (OTA server) is on top of ESP8266WebServer which is on top of WiFiServer.

The program is currently 1600 lines.  If someone wants it, I can send it or put it on my web server and post a link.  It reads 3 types of temp sensors, also reads Barometric Pressure and Humidity, writes to OLED and SD (history files) and sends out a web page with lots of information including an .svg graphic with 3 symbols and two text lines.  If the sensors are missing, it goes on with what it has.  I tried to make it not break so easily as some programs.


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