TCP packet latency between two photon over wifi

General
1

Hi,
I have two Photons, one for the TCP server code, the other TCP client code. Network is over local Wifi.

Server:

TCPServer server = TCPServer(3456);
TCPClient client;
unsigned long last_send = 0;

void setup(){
  server.begin();

  Serial.begin(115200);

}

void loop() {
  if (client.connected()) {
      
    if (millis() - last_send >= 100) {
        unsigned long temp = millis();
        last_send = temp / 100 * 100;
  
        server.printf("$%lu: {test}\n", temp);
    }  
      
    while (client.available()) {
      Serial.write(client.read());
    }
  } else {
    // if no client is yet connected, check for a new connection
    client = server.available();
  }
}

Client code:

SYSTEM_THREAD(ENABLED);
TCPClient client;
byte server[] = { 192, 168, 1, 111 };

void setup() {
  Serial.begin(115200);
}

void loop() {
  while (client.available()) {
    char c = client.read();
    if (c=='$') {
        Serial.printf("\n%lu: ", millis());
    };
    
    Serial.print(c);
  }

  if (!client.connected()){
    Serial.println();
    Serial.println("disconnecting.");
    client.stop();
    if (client.connect(server, 3456)) {
      Serial.println("connected");
    } else{
      Serial.println("connection failed");
    }
  }
}

So the idea is two send from the server to client every 100ms the current millis(), and we check if at the client side it receives it every 100ms or not.
As my result the clients sometimes receives from 20 ms - 200 ms. Attached the picture

09
091670×978 77.6 KB

How is it possible to receive the packets every 100 ms? Where is the problem? The server sends it too slow, or the router? or the problem with the client code?

Thanks

2

Maybe somebody has an answer for me?