Espressif ESP32-S2 User Manual

Chapter 2. API Reference
LWIP_TCP_RECCVMBOX_SIZE multiples the maximum TCP socket number. In other words, the
bigger LWIP_TCP_RECVMBOX_SIZE means more memory. On the other hand, if the receiv mail
box is too small, the mail box may be full. If the mail box is full, the LWIP drops the packets. So
generally we need to make sure the TCP receive mail box is big enough to avoid packet drop between
LWIP core and application.
Range:
• from 6 to 64 if CONFIG_LWIP_WND_SCALE
• from 6 to 1024 if CONFIG_LWIP_WND_SCALE
Default value:
• 6
CONFIG_LWIP_TCP_QUEUE_OOSEQ
Queue incoming out-of-order segments
Found in: Component config > LWIP > TCP
Queue incoming out-of-order segments for later use.
Disable this option to save some RAM during TCP sessions, at the expense of increased retransmissions
if segments arrive out of order.
Default value:
• Yes (enabled)
CONFIG_LWIP_TCP_SACK_OUT
Support sending selective acknowledgements
Found in: Component config > LWIP > TCP
TCP will support sending selective acknowledgements (SACKs).
Default value:
• No (disabled)
CONFIG_LWIP_TCP_KEEP_CONNECTION_WHEN_IP_CHANGES
Keep TCP connections when IP changed
Found in: Component config > LWIP > TCP
This option is enabled when the following scenario happen: network dropped and reconnected, IP
changes is like: 192.168.0.2->0.0.0.0->192.168.0.2
Disable this option to keep consistent with the original LWIP code behavior.
Default value:
• No (disabled)
CONFIG_LWIP_TCP_OVERSIZE
Pre-allocate transmit PBUF size
Found in: Component config > LWIP > TCP
Allows enabling“oversize”allocation of TCP transmission pbufs ahead of time, which can reduce the
length of pbuf chains used for transmission.
This will not make a difference to sockets where Nagle’s algorithm is disabled.
Default value of MSS is fine for most applications, 25% MSS may save some RAM when only trans-
mitting small amounts of data. Disabled will have worst performance and fragmentation characteristics,
but uses least RAM overall.
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Release v4.4

Espressif ESP32-S2 Specifications

General

Brand	Espressif
Model	ESP32-S2
Category	Single board computers
Language	English