ESP8266 failing post requests - arduino

Question

I'm hesitant to ask this on here; I have made an issue on GitHub, and I really need it resolved.
Basically, I'm sending posts to dweetPro every 15 seconds. It will work flawlessly for hours on end, then just randomly it will stop, send one successful one for every 20 failed responses.
I have tried everything I can think of, I'm pretty sure my code is right, not sure if it is something with the library or what. I can send the posts from Python on my PC indefinitely and never fails, so it's definitely on the ESP's side.
I'm using a clean 2A power supply, so it's not a power issue.
Here is the link of a couple Wireshark logs from the ESP sending posts. Both valid and invalid are on them.
One
Two
Some more info can be found on the issue on GitHub. This is the code I'm using, with debug lines used:
void send_to_server(String* time_sent, float magnitude, String status,
int earthquake_occured, float* data, int data_size)
{
int content_length;
String content = make_json_content(&content_length, magnitude,
status, earthquake_occured, data, data_size);
int s = -100;
int c = 0;
while (s<0 && c<10)
{
HTTPClient http;
http.setTimeout(1000);
bool suc = http.begin("http://dweetpro.io/v2/dweets");
Serial.print("Success?: "); Serial.println(suc);
http.addHeader("Content-Type", "application/json");
http.addHeader("Accept", "application/json");
http.addHeader("X-DWEET-AUTH", "xxx");
int timerr = millis();
Serial.println("Posting");
s = http.POST(content);
Serial.print("Posted: "); Serial.println(millis() - timerr);
Serial.print("Post len: "); Serial.println(s);
http.writeToStream(&Serial);
Serial.println("");
http.end();
++c;
}
Serial.println("Ended");
}
When successful, s prints 200, when failed, it print -1.
On Wireshark, every successful post will show data, but for unsuccessful posts, it will show some data for the first several failed ones, then it just stops. It's like it overloads itself or something.
Once again, sorry for this cluster of a question, but I just don't know what else to do. I have spent so much time on this with no end in sight. Thank you all so very much.
EDIT: Some other information I should have added is that if it isn't sending valid posts, I can reset the ESP and it will still not be working. Its really weird, that's why I am so at a loss. If it is on a roll sending valid posts, I can reset/unplug and it will work still. If it isn't working and I do the same, it won't be working still.
Is there any chance that it could just be some sort of interference at my home location?

Answer 1

Anytime I hear about an Arduino project that crashes after some time and I see the String class I get suspicious of it right away. In older versions for the Arduino it had a nasty memory leak. Current versions have fixed that leak but still leave the problem with concatenation. Basically, when you concatenate two Strings it has to deallocate the spot in memory where they were and allocate new space for the larger String. If nothing else has gone on the heap or stack since the last concatenation then that might not be a problem.
But what happens is that someone is building two Strings that are both growing larger and larger. And each time it has to allocate that memory further and further up in memory, leaving holes where the smaller Strings used to be. Eventually, the heap looks like swiss cheese and there's no garbage collection to come through and defragment it. After the project has run fine for quite some time then suddenly the heap and the stack get together and it's lights out.
I don't know if there is a function like freemem for the Arduino that works for the ESP8266, but it would be worth looking into finding a way to find out how much free memory you have. If it is steadily shrinking to 0 as the program runs then you've found your problem.