From 0aa1ba251f325c79f4b0dc1662c49d5c1c56d2a2 Mon Sep 17 00:00:00 2001
From: agessaman <adam@gessaman.com>
Date: Wed, 11 Nov 2026 17:15:32 -0800
Subject: [PATCH] fix(webconfig): rebind port 80 right after a stop

A closed HTTP connection holds port 80 in TIME_WAIT for 2*MSL,
so the next listen fails with ERR_USE. Set SOF_REUSEADDR on the
new pcb before tcp_bind, and only for port 80, via a linker wrap.
---
 platformio.ini                    |  2 ++
 src/helpers/ESP32TcpBindReuse.cpp | 29 +++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)
 create mode 100644 src/helpers/ESP32TcpBindReuse.cpp

diff --git a/platformio.ini b/platformio.ini
index ea86a1f73d..197500a2dc 100644
--- a/platformio.ini
+++ b/platformio.ini
@@ -75,6 +75,8 @@ build_flags = ${arduino_base.build_flags}
   -Wl,--wrap=esp_transport_ws_init
   ; Run dns_gethostbyname on the lwIP thread; see src/helpers/ESP32DnsThreadFix.cpp.
   -Wl,--wrap=dns_gethostbyname
+  ; Rebind port 80 during TIME_WAIT; see src/helpers/ESP32TcpBindReuse.cpp.
+  -Wl,--wrap=tcp_bind
 ;  -D ESP32_CPU_FREQ=80          ; change it to your need
 build_src_filter = ${arduino_base.build_src_filter}
   +<helpers/esp32/WebConfigServer.cpp>   ; empty TU unless WITH_MQTT_BRIDGE
diff --git a/src/helpers/ESP32TcpBindReuse.cpp b/src/helpers/ESP32TcpBindReuse.cpp
new file mode 100644
index 0000000000..e61571b218
--- /dev/null
+++ b/src/helpers/ESP32TcpBindReuse.cpp
@@ -0,0 +1,29 @@
+// Lets a new port-80 listener bind while an old HTTP connection is still in TIME_WAIT.
+
+#ifdef ESP_PLATFORM
+
+#include <lwip/opt.h>
+#include <lwip/ip.h>
+#include <lwip/tcp.h>
+
+// Arduino 2.0.17 names the switch SO_REUSE; later cores name it LWIP_SO_REUSE.
+#ifndef LWIP_SO_REUSE
+#ifdef SO_REUSE
+#define LWIP_SO_REUSE SO_REUSE
+#else
+#define LWIP_SO_REUSE 0
+#endif
+#endif
+
+extern "C" err_t __real_tcp_bind(struct tcp_pcb* pcb, const ip_addr_t* ipaddr, u16_t port);
+
+extern "C" err_t __wrap_tcp_bind(struct tcp_pcb* pcb, const ip_addr_t* ipaddr, u16_t port) {
+#if LWIP_SO_REUSE
+  if (pcb != NULL && port == 80) {
+    ip_set_option(pcb, SOF_REUSEADDR);
+  }
+#endif
+  return __real_tcp_bind(pcb, ipaddr, port);
+}
+
+#endif  // ESP_PLATFORM