ESP32 Forum

"WiFiTelnetToSerial" example not work as expect(I have test it on esp32c3 and esp32 modules,like same),when I send data from another device to esp32,the data can't recieve immediately，maybe five or ten seconds it will show in the terminal,or can't show at all,but if I send data from esp32 to another device then the data will recieve by esp32 quickly.




The next is sample code,

/*
WiFiTelnetToSerial - Example Transparent UART to Telnet Server for ESP32

Copyright (c) 2017 Hristo Gochkov. All rights reserved.
This file is part of the ESP32 WiFi library for Arduino environment.

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <WiFi.h>
#include <WiFiMulti.h>

WiFiMulti wifiMulti;

//how many clients should be able to telnet to this ESP32
#define MAX_SRV_CLIENTS 1
const char* ssid = "********"; //I have used mine ssid,left is modified to ****
const char* password = "*******";

WiFiServer server(23);
WiFiClient serverClients[MAX_SRV_CLIENTS];

void setup() {
Serial.begin(115200);
Serial.println("\nConnecting");

wifiMulti.addAP(ssid, password);
//wifiMulti.addAP("ssid_from_AP_2", "your_password_for_AP_2");
//wifiMulti.addAP("ssid_from_AP_3", "your_password_for_AP_3");

Serial.println("Connecting Wifi ");
for (int loops = 10; loops > 0; loops--) {
if (wifiMulti.run() == WL_CONNECTED) {
Serial.println("");
Serial.print("WiFi connected ");
Serial.print("IP address: ");
Serial.println(WiFi.localIP());
break;
}
else {
Serial.println(loops);
delay(1000);
}
}
if (wifiMulti.run() != WL_CONNECTED) {
Serial.println("WiFi connect failed");
delay(1000);
ESP.restart();
}

//start UART and the server
//Serial1.begin(9600);
server.begin();
server.setNoDelay(true);

Serial.print("Ready! Use 'telnet ");
Serial.print(WiFi.localIP());
Serial.println(" 23' to connect");
}

void loop() {
uint8_t i;
if (wifiMulti.run() == WL_CONNECTED) {
//check if there are any new clients
if (server.hasClient()){
for(i = 0; i < MAX_SRV_CLIENTS; i++){
//find free/disconnected spot
if (!serverClients || !serverClients.connected()){
if(serverClients) serverClients.stop();
serverClients = server.available();
if (!serverClients) Serial.println("available broken");
Serial.print("New client: ");
Serial.print(i); Serial.print(' ');
Serial.println(serverClients.remoteIP());
break;
}
}
if (i >= MAX_SRV_CLIENTS) {
//no free/disconnected spot so reject
server.available().stop();
}
}
//check clients for data
for(i = 0; i < MAX_SRV_CLIENTS; i++){
if (serverClients && serverClients.connected()){
if(serverClients.available()){
//get data from the telnet client and push it to the UART
while(serverClients[i].available()) Serial.write(serverClients[i].read());
}
}
else {
if (serverClients[i]) {
serverClients[i].stop();
}
}
}
//check UART for data
if(Serial.available()){
size_t len = Serial.available();
uint8_t sbuf[len];
Serial.readBytes(sbuf, len);
//push UART data to all connected telnet clients
for(i = 0; i < MAX_SRV_CLIENTS; i++){
if (serverClients[i] && serverClients[i].connected()){
serverClients[i].write(sbuf, len);
delay(1);
}
}
}
}
else {
Serial.println("WiFi not connected!");
for(i = 0; i < MAX_SRV_CLIENTS; i++) {
if (serverClients[i]) serverClients[i].stop();
}
delay(1000);
}
}



next is the message show of esp32 output:

ets Jul 29 2019 12:21:46
16:31:02.752 ->
16:31:02.752 -> rst:0x1 (POWERON_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
16:31:02.752 -> configsip: 0, SPIWP:0xee
16:31:02.752 -> clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
16:31:02.752 -> mode:DIO, clock div:1
16:31:02.752 -> load:0x3fff0030,len:1420
16:31:02.752 -> ho 0 tail 12 room 4
16:31:02.752 -> load:0x40078000,len:13540
16:31:02.752 -> load:0x40080400,len:3604
16:31:02.752 -> entry 0x400805f0
16:31:02.988 ->
16:31:02.988 -> Connecting
16:31:02.988 -> Connecting Wifi
16:31:14.021 -> 10
16:31:15.030 ->
16:31:15.030 -> WiFi connected IP address: 192.168.2.126
16:31:15.030 -> Ready! Use 'telnet 192.168.2.126 23' to connect
16:32:03.054 -> New client: 0 192.168.2.139 //comment by user,"next message is show after I send it and type some data in the uart terminal to send "
16:32:15.639 -> dddddddddddddddd