cat-in-136
commented
2 years ago Sometimes the first six bytes of 220--- is sent on the only packet.
This boundary is come from the execution unit of client.print().
client.print(F("220---")); client.print(welcomeMessage); client.println(F(" ---"));So this issue can be resolved by storing the message in a buffer and sending it to the client when all messages stored. For example, the following workaround code:
template <size_t N = 256>
class StringPrintBuffer : public Print {
public:
virtual size_t write(const uint8_t *buffer, size_t size) override {
if (_size + size < N) {
memcpy(_buf + _size, buffer, size);
_size += size;
return size;
} else {
return 0;
}
}
virtual size_t write(uint8_t c) override {
if (_size < N) {
_buf[_size++] = c;
return 1;
} else {
return 0;
}
}
const char* buffer() { return reinterpret_cast<const char*>(_buf); };
const size_t size() { return _size; };
private:
size_t _size = 0;
uint8_t _buf[N] = {0};
};
// ...snip...
StringPrintBuffer<256> response;
response.print(F("220---")); response.print(welcomeMessage); response.println(F(" ---"));
response.println(F("220--- By Renzo Mischianti ---"));
response.print(F("220 -- Version ")); response.print(FTP_SERVER_VERSION); response.println(F(" --"));
client.write(response.buffer(), response.size());This can occur in any other response and it is necessary to apply the change to all responses.
xreef
where 192.168.0.4 is my linux PC (ftp client), 192.168.0.64 is M5Stack. RST were generated by gftp. Line 78-89 were generated by gftp's connection retry.
LFrank2021
Some FTP clients such as gftp sometimes sends an RST packet and disconnect the TCP session before receiving all
220--responses just after connecting.The first
220-responses are consisting of the following 112 bytes (whenwelcomeMessageis default):Subsequent messages are similar. This behavior depends on esp32 library's Nagle algorithm implementation.
When the messages are segmented excessively and there is a certain large latency between the server (esp32) and the client, some client seems to send an RST packet to disconnect.