Multiple client server over wifi

Question

Trying to setup a server on Arduino to support multiple clients, I am able to support one but I don't want to flush that client to make another connection.

#include <ESP8266WiFi.h>
const char* ssid = "your-ssid";
const char* password = "your-password";
// Create an instance of the server
// specify the port to listen on as an argument
WiFiServer server(80);

void setup() {
  Serial.begin(115200);
  delay(10);

  // prepare GPIO2
  pinMode(2, OUTPUT);
  digitalWrite(2, 0);

  // Connect to WiFi network
  Serial.println();
  Serial.println();
  Serial.print("Connecting to ");
  Serial.println(ssid);
  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("");
  Serial.println("WiFi connected");

  // Start the server
  server.begin();
  Serial.println("Server started");

  // Print the IP address
  Serial.println(WiFi.localIP());
}

void loop() {
  // Check if a client has connected
  WiFiClient client = server.available();
  if (!client) {
    return;
  }

  // Wait until the client sends some data
  Serial.println("new client");
  while(!client.available()){
    delay(1);
  }

  // Read the first line of the request
  String req = client.readStringUntil('\r');
  Serial.println(req);
  client.flush();

  // Match the request
  int val;
  if (req.indexOf("/gpio/0") != -1)
    val = 0;
  else if (req.indexOf("/gpio/1") != -1)
    val = 1;
  else {
    Serial.println("invalid request");
    client.stop();
    return;
  }

  // Set GPIO2 according to the request
  digitalWrite(2, val);

  client.flush();

  // Prepare the response
  String s = "HTTP/1.1 200 OK\r\nContent-Type: text/html\r\n\r\n<!DOCTYPE HTML>\r\n<html>\r\nGPIO is now ";
  s += (val)?"high":"low";
  s += "</html>\n";

  // Send the response to the client
  client.print(s);
  delay(1);
  Serial.println("Client disonnected");

  // The client will actually be disconnected 
  // when the function returns and 'client' object is detroyed
}

Using this code, the server handles only one client at a time, but I need to connect multiple clents simultaneously.

Mark Smith · Answer 1 · 2016-11-16T21:14:36.303

You need to keep track of multiple WiFiClients - declare an array of them, for example, and each time server.available() gives you a new one, store it in the array.

Then you need to make sure your code doesn't stick waiting for data from each item. You could service each WifiClient in turn: if it has data waiting (client[i].available() is true), read the data (client[i].read()) and store it. When you get a \r from a client, you know you have a whole line, and you can process it.

Here's a nearly-complete (but untested) example so you can see what I'm talking about. Naturally it's not the only way to do it.

#include <ESP8266WiFi.h>
const char* ssid = "your-ssid";
const char* password = "your-password";
#define MAX_CLIENTS 10
#define MAX_LINE_LENGTH 50
// Create an instance of the server
// specify the port to listen on as an argument
WiFiServer server(80);
WiFiClient *clients[MAX_CLIENTS] = { NULL };
char inputs[MAX_CLIENTS][MAX_LINE_LENGTH] = { 0 };

void setup() {
  Serial.begin(115200);
  delay(10);

  // prepare GPIO2
  pinMode(2, OUTPUT);
  digitalWrite(2, 0);

  // Connect to WiFi network
  Serial.println();
  Serial.println();
  Serial.print("Connecting to ");
  Serial.println(ssid);
  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("");
  Serial.println("WiFi connected");

  // Start the server
  server.begin();
  Serial.println("Server started");

  // Print the IP address
  Serial.println(WiFi.localIP());
}

void loop() {
  // Check if a new client has connected
  WiFiClient newClient = server.available();
  if (client) {
    Serial.println("new client");
    // Find the first unused space
    for (int i=0 ; i<MAX_CLIENTS ; ++i) {
        if (NULL == clients[i]) {
            clients[i] = new WiFiClient(newClient);
            break;
        }
     }
  }

  // Check whether each client has some data
  for (int i=0 ; i<MAX_CLIENTS ; ++i) {
    // If the client is in use, and has some data...
    if (NULL != clients[i] && clients[i]->available() ) {
      // Read the data 
      char newChar = clients[i]->read();

      // If we have the end of a string
      // (Using the test your code uses)
      if ('\r' == newChar) {
        // Blah blah, do whatever you want with inputs[i]

        // Empty the string for next time
        inputs[i][0] = NULL;

        // The flush that you had in your code - I'm not sure
        // why you want this, but here it is
        clients[i]->flush();

        // If you want to disconnect the client here, then do this:
        clients[i]->stop();
        delete clients[i];
        clients[i] = NULL;

      } else {
        // Add it to the string
        strcat(inputs[i], newChar);
        // IMPORTANT: Nothing stops this from overrunning the string and
        //            trashing your memory. You SHOULD guard against this.
        //            But I'm not going to do all your work for you :-)
      }
    }
  }

}

Bhushan Mahajan · Answer 2 · 2019-04-18T18:07:18.240

Here , I have used array of WiFiClient . The reason is array pointer will hold previous plus latest WiFiClients (emoteIP and remotePort ) and user will be able to choose which WIFiClient to be used for communication.

We can store IPAddress , Port as well as whole WiFiClient object in an array

 //===========================================
       WebServer  Wserver(80);

       WiFiClient Wclient;



       WiFiClient *Wificlients[10] = { NULL };

       int  Clientindex=-1;


       Wclient = Wserver.client(); // or  server.avilable() if WiFiServer

       Wificlients[Clientindex++]=new WiFiClient(Wclient);

       int   cntloggedinclient=0;
       int kk=0;

       while(Wificlients[kk] != NULL)
           {
               cntloggedinclient++;  // Total clients count
               kk++;
           }


         // Multicasting bytes to all connected clients.
         int kkk =0;
         while(kkk<cntloggedinclient)
         {
           Wificlients[kkk]->write((unsigned char*) &newbuff,len);
           kkk++;    
         }

score -1 · Answer 3 · answered Dec 09 '22 at 03:47

I have a solution using RTOS Tasks, I think this is the best way to manage multiple clients at same time. I test this code in ESP32 dev module.

#if CONFIG_FREERTOS_UNICORE
#define ARDUINO_RUNNING_CORE 0
#else
#define ARDUINO_RUNNING_CORE 1
#endif
#include <WiFi.h>
const char* ssid = "[YOUR-NETWORK-SSID]";
const char* password = "[YOUR-SSID-PASSWORD]";
void TaskClientSocket( void *pvParameters );
WiFiServer wifiServer(80);
void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  delay(1000);
  WiFi.begin(ssid,password);
  Serial.println("Connecting to Wifi...");
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.print(".");
  }
  Serial.println("Connected to WiFi network");
  Serial.println(WiFi.localIP());
wifiServer.begin();
}
void loop() {
  WiFiClient client = wifiServer.available();
  if( client){
    Serial.println("New Client Connected...");
    xTaskCreatePinnedToCore(
    TaskClientSocket
    ,  "TaskClientSocket"
    ,  4098
    ,  &client
    ,  2

    ,  NULL 
    ,  ARDUINO_RUNNING_CORE);
  }
}
void TaskClientSocket( void pvParameters )
{
    WiFiClient clientHandle = ((WiFiClient*)pvParameters);
    for (;;) 
    {
      while(clientHandle.connected()){
        while(clientHandle.available()>0){
          char c = clientHandle.read();
          clientHandle.write(c); 
        }
        vTaskDelay(100);
      }
      clientHandle.stop();
      Serial.println("Client disconnected");
      vTaskDelete(NULL);
    }
}

Multiple client server over wifi

3 Answers3