Sending multiple messages over the serial monitor in nodeMCU

Question

I am trying to send multiple messages wirelessly from one ESP8266-12E NodeMCU to another. I have successfully established the connection and am able to send and receive single messages. The MAC addresses are solely for the verification that the data is going to the right client. My trouble is sending multiple messages which I should be able to observe in the serial monitor.

Here's my server code:

#include <ESP8266WiFi.h>
extern "C" {
 #include <user_interface.h>
}
int32_t freq = 10000;
WiFiServer server(80); //Initialize the server on Port 80
void setup() {
 pinMode(D1,OUTPUT);
 pinMode(D2,OUTPUT);
 pinMode(D3,OUTPUT);
 Serial.begin(9600); //Start communication between the ESP8266-12E and the monitor window
 analogWriteFreq(freq);
 WiFi.mode(WIFI_AP); //This ESP8266-12E is an AccessPoint 
 WiFi.softAP("NodeMCU_js", "12345678"); //Provide the (SSID, password) 
 IPAddress HTTPS_ServerIP = WiFi.softAPIP(); //Obtain the IP of the Server
 Serial.println("Server IP is: "); //Print the IP to the monitor window 
 Serial.println(HTTPS_ServerIP);
 server.begin(); //Start the HTTP Server
}
void loop() { 
 WiFiClient client = server.available(); //Check if a client has connected to the server
 struct station_info *stat_info;
 struct ip_addr *IPaddress;
 IPAddress address;
 if (client) { 
 Serial.println("Somebody has connected :)");
 stat_info = wifi_softap_get_station_info();
 while (stat_info != NULL){
 IPaddress = &stat_info->ip;
 address = IPaddress->addr;
 Serial.println();
 Serial.print("Client IP Address = ");
 Serial.print(address);
 Serial.println();
 Serial.print("Client MAC Address = ");
 Serial.print(stat_info->bssid[0],HEX);
 Serial.print(":");
 Serial.print(stat_info->bssid[1],HEX);
 Serial.print(":");
 Serial.print(stat_info->bssid[2],HEX);
 Serial.print(":");
 Serial.print(stat_info->bssid[3],HEX);
 Serial.print(":");
 Serial.print(stat_info->bssid[4],HEX);
 Serial.print(":");
 Serial.print(stat_info->bssid[5],HEX);
 Serial.println();
 if (stat_info->bssid[0] == 0xDC && stat_info->bssid[1] == 0x4F && stat_info->bssid[2] == 0x22 && stat_info->bssid[3] == 0x17 && stat_info->bssid[4] == 0xEE && stat_info->bssid[5] == 0x95){
 int duty1 = 150;
 int duty2 = 200;
 int duty3 = 250;
 Serial.println("Duty - 1 : "+String(duty1));
 Serial.println("Duty - 2 : "+String(duty2));
 Serial.println("Duty - 3 : "+String(duty3));
 analogWrite(D1,duty1);
 analogWrite(D2,duty2);
 analogWrite(D3,duty3);
 client.println(String(duty1)+"\r"); //Server's response to the client
 client.println(String(duty2)+"\r");
 client.println(String(duty3)+"\r");
 }
 else {
 Serial.println();
 Serial.println("Client not recognized.");
 }
 stat_info = STAILQ_NEXT(stat_info, next); 
 }
 }
}

Here's my client code:

#include <ESP8266WiFi.h>
#include <ESP8266HTTPClient.h>
char ssid[] = "NodeMCU_js";
char password[] = "12345678";
IPAddress server(192,168,4,1); // the fix IP address of the server
WiFiClient client; // Creates a client that can connect to to a specified internet IP address and port as defined in client.connect()
void setup() {
 pinMode(D4,OUTPUT);
 WiFi.persistent(false);
 WiFi.mode(WIFI_STA);
 Serial.begin(9600); //Serial connection
 WiFi.begin(ssid,password); //WiFi connection
 while (WiFi.status() != WL_CONNECTED) { //Wait for the WiFI connection completion
 delay(500);
 Serial.println("Connecting...");
 }
 Serial.println("Connected.");
 client.connect(server,80);
}
void loop() {
 if(WiFi.status()== WL_CONNECTED){ //Check WiFi connection status
 String answer1 = client.readStringUntil('\r');
 Serial.println();
 Serial.print("From Server(1): ");
 Serial.print(answer1);
 client.flush();
 String answer2 = client.readStringUntil('\r');
 Serial.println();
 Serial.print("From Server(2): ");
 Serial.print(answer2);
 client.flush();
 String answer3 = client.readStringUntil('\r');
 Serial.println();
 Serial.print("From Server(3): ");
 Serial.print(answer3);
 client.flush();
 }
 else{
 Serial.println("Error in WiFi connection"); 
 } 
} 

It would be helpful if I could get the correct way of doing this.

Thanks in advance.

• Juraj: println sends \r\n. read until \n. flush() waits until data are send. you do not send data from client. why do you use flush?
• Dingodudesir: flush() is used for waiting till transmission is completed. It can be used at server or client.
• Juraj: you do not transmit from client. only receive.
• Dingodudesir: I am receiving at the client, as per my client code. Is it recommended to remove flush() at the client?
• Dingodudesir: So I removed the flush() from the client sie and used it at the server. The problem still persists.

Answer 1

from server you send at the end of line \r\r\n. first \r is in the string and \r\n is added by println. then at the client you read until \r the first line, the you read an empty line until next \r.