--- The client throttles connection by decreasing its window: ---
[13:25:18.078] lwip: ip_input: iphdr->dest 0x42d363a7 netif->ip_addr 0x200c80a (0xd063a7, 0xc80a, 0x42030000)
(from client) [ACK] Seq=117 Ack=338819 Win=270 Len=0

--- lwip sends the last chunk of data that fits the window: ---
[13:25:18.609] lwip: tcp_output_segment: 345329:345599
(from lwip) [TCP Window Full] [TCP segment of a reassembled PDU]

--- The client informs that the window is zero: ---
[13:25:18.734] lwip: ip_input: iphdr->dest 0x42d363a7 netif->ip_addr 0x200c80a (0xd063a7, 0xc80a, 0x42030000)
(from client) [TCP ZeroWindow] [ACK] Seq=117 Ack=339089 Win=0 Len=0

--- Apparently lwip wonders if the window is still zero: ---
[13:25:19.218] lwip: tcp_zero_window_probe: tcp_ticks 8   pcb->tmr 5 pcb->keep_cnt_sent 0
(from lwip) [TCP ZeroWindowProbe] [TCP segment of a reassembled PDU]

--- Client says it's still zero: ---
[13:25:19.218] lwip: ip_input: iphdr->dest 0x42d363a7 netif->ip_addr 0x200c80a (0xd063a7, 0xc80a, 0x42030000)
(from client) [TCP ZeroWindowProbeAck] [TCP ZeroWindow] [ACK] Seq=117 Ack=339089 Win=0 Len=0

--- The client decides to resume the transfer and sends a window update: ---
[13:25:19.250] lwip: ip_input: iphdr->dest 0x42d363a7 netif->ip_addr 0x200c80a (0xd063a7, 0xc80a, 0x42030000)
[TCP Window Update] [ACK] Seq=117 Ack=339089 Win=65535 Len=0

--- lwip sends 21 data packets to the client: ---
[13:25:19.250] lwip: tcp_output_segment: 345599:346761
[13:25:19.250] lwip: tcp_output_segment: 346761:348193 // Sequence number: 340251 (as per Wireshark)
[13:25:19.250] lwip: tcp_output_segment: 348193:349625
[13:25:19.250] lwip: tcp_output_segment: 349625:351057
[13:25:19.250] lwip: tcp_output_segment: 351057:352489
[13:25:19.250] lwip: tcp_output_segment: 352489:353921
[13:25:19.250] lwip: tcp_output_segment: 353921:355353
[13:25:19.250] lwip: tcp_output_segment: 355353:356785
[13:25:19.250] lwip: tcp_output_segment: 356785:358217
[13:25:19.250] lwip: tcp_output_segment: 358217:359649
[13:25:19.250] lwip: tcp_output_segment: 359649:361081
[13:25:19.250] lwip: tcp_output_segment: 361081:362513
[13:25:19.250] lwip: tcp_output_segment: 362513:363945
[13:25:19.250] lwip: tcp_output_segment: 363945:365377
[13:25:19.250] lwip: tcp_output_segment: 365377:366809
[13:25:19.250] lwip: tcp_output_segment: 366809:368241
[13:25:19.250] lwip: tcp_output_segment: 368241:369673
[13:25:19.250] lwip: tcp_output_segment: 369673:371105
[13:25:19.250] lwip: tcp_output_segment: 371105:372537
[13:25:19.250] lwip: tcp_output_segment: 372537:373969
[13:25:19.250] lwip: tcp_output_segment: 373969:374799

--- This ACK (340251) will be sent twice by the client: ---
[13:25:19.437] lwip: ip_input: iphdr->dest 0x42d363a7 netif->ip_addr 0x200c80a (0xd063a7, 0xc80a, 0x42030000)
(from client) [ACK] Seq=117 Ack=340251 Win=64373 Len=0

--- Some more data from lwip flying in: ---
[13:25:19.437] lwip: tcp_output_segment: 374799:375961
(from lwip) [TCP segment of a reassembled PDU]

--- The last packet that client sends to lwip is repeating the ACK 340251 again: ---
[13:25:19.437] lwip: ip_input: iphdr->dest 0x42d363a7 netif->ip_addr 0x200c80a (0xd063a7, 0xc80a, 0x42030000)
(from client) [TCP Dup ACK 479#1] [ACK] Seq=117 Ack=340251 Win=64373 Len=0

--- Here LwIP tries to talk to the client, the client ignores all keepalives and retransmissions: ---
[13:25:20.218] lwip: tcp_output_segment: 346761:348193
(from lwip) [TCP Retransmission] [TCP segment of a reassembled PDU]

[13:25:21.828] lwip: tcp_output_segment: 346761:348193
(from lwip) [TCP Retransmission] [TCP segment of a reassembled PDU]

[13:25:24.640] lwip: tcp_keepalive: sending KEEPALIVE probe to 10.200.0.1
(from lwip) [TCP Keep-Alive] [ACK] Seq=369450 Ack=117 Win=11564 Len=0

[13:25:25.046] lwip: tcp_output_segment: 346761:348193
(from lwip) [TCP Retransmission] [TCP segment of a reassembled PDU]

[13:25:29.671] lwip: tcp_keepalive: sending KEEPALIVE probe to 10.200.0.1
(from lwip) [TCP Keep-Alive] [ACK] Seq=369450 Ack=117 Win=11564 Len=0

[13:25:31.484] lwip: tcp_output_segment: 346761:348193
(from lwip) [TCP Retransmission] [TCP segment of a reassembled PDU]

[13:25:34.703] lwip: tcp_keepalive: sending KEEPALIVE probe to  10.200.0.1
(from lwip) [TCP Keep-Alive] [ACK] Seq=369450 Ack=117 Win=11564 Len=0

--- LwIP gives up after 15 seconds as configured in my project (3 keepalives with 5s interval): ---
[13:25:39.734] lwip: tcp_slowtmr: KEEPALIVE timeout. Aborting connection to 10.200.0.1
[13:25:39.734] lwip: tcp_pcb_purge: not all data sent
[13:25:39.734] lwip: tcp_pcb_purge: data left on ->unacked
(from lwip) [RST, ACK] Seq=369451 Ack=117 Win=41005 Len=0
[13:25:39.734] lwip: lwip_tcp_err_callback, err=-13

--- Client sends ACK to the RST packet (so it's alive?): ---
[13:25:39.734] lwip: ip_input: iphdr->dest 0x42d363a7 netif->ip_addr 0x200c80a (0xd063a7, 0xc80a, 0x42030000)
(from client) [TCP Dup ACK 479#2] [ACK] Seq=117 Ack=340251 Win=64373 Len=0

LwIP sends the final [RST, ACK] after that.
(from lwip) [RST, ACK] Seq=340251 Ack=117 Win=41005 Len=0