I have an ESP32 application that uses a web server as a user interface. For auditing and debugging during development I use Serial; however, that is impractical in the installed system. So, I decided to use Telnet (TCP/IP) to monitor what is happening when Serial is impractical.
The issue is that once a TCP/IP session has been established, when a HTTP request is received, the TCP/IP session is aborted.
I have reproduced the issue in a minimal sketch here:
#include "Arduino.h"
#include <WiFi.h>
#include <WiFiClient.h>
#include <WebServer.h>
WiFiClient telnetClient;
WebServer server(80);
WiFiServer telnetServer(23);
void telnetPrint(const char* text)
{
if (telnetClient)
{
telnetClient.print(text);
}
}
void telnetPrintln(const char *text)
{
telnetPrint(text);
telnetPrint("\r\n");
}
void _print(const char* text)
{
Serial.print(text);
telnetPrint(text);
}
void _println(const char* text)
{
Serial.println(text);
telnetPrintln(text);
}
void _println(IPAddress myIP)
{
char rgIPTxt[32];
sprintf(rgIPTxt,"%u.%u.%u.%u",myIP[0],myIP[1],myIP[2],myIP[3]);
_println(rgIPTxt);
}
const char *rootFmt="\
<html>\
<head>\
<title>Test</title>\
</head>\
<body>\
<h1>Test</h1>\
<div>\
<h2>Heap size=%d<br><br>\
</div>\
</body>\
</html>\
";
char rootMessage[1024];
void updateRootMessage()
{
_println("updateRoot");
snprintf(rootMessage, sizeof(rootMessage), rootFmt,
heap_caps_get_free_size(MALLOC_CAP_8BIT)
);
}
void handleRoot()
{
_println("Entered handleRoot");
updateRootMessage();
server.send(200, "text/html", rootMessage);
_println("Leaving handleRoot");
}
void wifiSTASetup(const char*ssid, const char*password)
{
WiFi.mode(WIFI_AP_STA);
WiFi.begin(ssid, password);
telnetServer.begin();
telnetClient=telnetServer.available();
_println("");
// Wait for connection
while (WiFi.status() != WL_CONNECTED)
{
delay(500);
_print(".");
}
_println("");
_print("Connected to ");
_println(ssid);
_print("IP address: ");
_println(WiFi.localIP());
server.on("/", handleRoot);
server.begin();
}
#define BAND 915E6
void setup()
{
Serial.begin(115200);
wifiSTASetup("your ssid", "your password");
}
void loop()
{
server.handleClient();
if (!telnetClient)
{
telnetClient=telnetServer.available();
if (telnetClient)
{
_println("telnetClient obtained");
}
}
}
