On my ESP32 I am trying to connect to my HomeAssistant server using ArduinoHA library.
I can easily connect when hard-coding the credentials: mqtt.begin("server", "username", "password");
But I recently tried to move the credentials to a config file that I read on setup:
typedef struct {
String url;
String username;
String password;
} Credentials;
Credentials creds = readCredentials(credsFile);
mqtt.begin(creds.url.c_str(), creds.username.c_str(), creds.password.c_str());
The connection fails and the MQTT state returns -2 (StateConnectionFailed).
I tried comparing the read values to the hard-coded values:
Serial.println(strcmp("192.168.1.45", creds.url.c_str()));
Serial.println(strcmp("username", creds.username.c_str()));
Serial.println(strcmp("passwird", creds.password.c_str()));
But it all returns 0 (i.e., its the same string).
Out of curiosity I tried it without reading the config file, and got same result:
String url = "192.168.1.45";
String username = "username";
String password = "password";
mqtt.begin(url.c_str(), username.c_str(), password.c_str());
So, does anyone know why the connection fails when using String object? Is there something I am missing?
== EDIT ==
It seems that the issue is memory related, the Strings are deleted before mqtt uses them to connect.
So I tried extracting the char* from the String object, but still got the same result:
String urlStr = String("192.168.1.45");
char url[urlStr.length() + 1];
strcpy(url, urlStr.c_str());
String usernameStr = String("username");
char username[usernameStr.length() + 1];
strcpy(username, usernameStr.c_str());
String passwordStr = String("password");
char password[passwordStr.length() + 1];
strcpy(password, passwordStr.c_str());
mqtt.begin(url, username, password);
One interesting thing I noticed is that using const char* instead of String does work, but I guess its just the compiler converting it to the original hard-coded version.
The only thing that worked for me is to define the Credentials object as a global variable, that way the credentials won't be cleared from memory.
