ESP8266 TCP/IP communication

Question

So I'm looking into having a TCP communication between 1 ESP8266 Chip (Station) and 2 ESP8266 (Clients) connected to that station. Every time I find a code including the TCP, they only include things like client.print(). But how can I write a message to a certain IP address in that network.

When I do client.print() it sends the message to ALL the clients. But I want to be able to do something like client1.print() and client2.print()

Answer 1

WiFiClient object wraps a TCP socket. A normal TCP socket is connected to IP address and port. WiFiServer starts a listening socket on a port. If server on listening socket is contacted by a remote client socket, it creates a local socket connected with the remote client socket on a free port and returns a WiFiClient object wrapping the socket. Everything you write or print to a WiFiClient is send to that one remote socket.

If one of your client boards creates a WiFiClient and connects it to IP address and port of the WiFiServer on your 'server' board, then you get there a WiFiClient from server.available() and this two WiFiClient objects are connected. What you write/print on one side you read only from the WiFiClient object on the other side.

client socket

if (client.connect(serverIP, PORT)) {
  client.print("request\n");
  String response = client.readStringUntil('\n');
  Serial.println(response);
  client.stop();
}

server side

WiFiClient client = server.available();
if (client && client.connected()) {
  String request = client.readStringUntil('\n');
  Serial.println(request);
  client.print("response\n");
  client.stop();
}