Poor performance over WiFi on ESP32

[zshivers]

It appears to take about ~300 ms to call one RPC over WiFi. I'm using an Adafruit ESP32-S2 TFT Feather board.

Arduino code:

#include <WiFi.h>
#include <simpleRPC.h>

#define SSID "..."
#define PASS "..."
#define PORT 1025

WiFiServer server(PORT);

void setup() {
  WiFi.begin(SSID, PASS);

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
  }

  server.begin();
}

void loop() {
  WiFiClient client{ server.available() };

  if (client) {
    while (client.connected()) {
      interface(
        client,
        millis, F("millis: Get time in milliseconds. @return: Timestamp in milliseconds"));
    }
    client.stop();
  }
}

Using a quick script to query millis() continuously:

from simple_rpc import Interface
with Interface('socket://REPLACE_IP:1025') as interface:
    last_millis = 0
    while True:
        millis = interface.millis()
        if last_millis > 0:
            print(millis - last_millis)
        last_millis = millis

results in approximately 300 ms between timestamps from the Arduino:

% python3 rpc_test.py
322
318
321
347
345
328
316
326
327
324
346
...

Trying something similar using Serial instead of WiFiClient as the Stream interface for the RPC results 0-1 ms between calls. Is there something that can be done to improve the latency?

[jfjlaros]

I think this may be related to this issue. Perhaps you can try the suggestion made there?