diff --git a/examples/arduino/w5500-mqtt/mongoose_custom.h b/examples/arduino/w5500-mqtt/mongoose_custom.h
index 78b4ca57..46a59819 100644
--- a/examples/arduino/w5500-mqtt/mongoose_custom.h
+++ b/examples/arduino/w5500-mqtt/mongoose_custom.h
@@ -11,5 +11,5 @@
 #define MG_ENABLE_SOCKET 0
 #define MG_ENABLE_TCPIP 1
 #define mkdir(a, b) (-1)
-#define MG_IO_SIZE 128
+#define MG_IO_SIZE 512
 //#define MG_ENABLE_LOG 0
diff --git a/examples/arduino/w5500-mqtt/net.c b/examples/arduino/w5500-mqtt/net.c
new file mode 100644
index 00000000..07f90dd9
--- /dev/null
+++ b/examples/arduino/w5500-mqtt/net.c
@@ -0,0 +1,58 @@
+#include "net.h"
+
+#define MQTT_SERVER "mqtt://broker.hivemq.com:1883"
+struct mg_connection *mqtt_connection;
+const char *mqtt_subscribe_topic = "mg/rx";
+const char *mqtt_publish_topic = "mg/tx";
+
+struct mg_mgr mgr;  // Mongoose event manager
+struct mg_tcpip_if mif = {.mac = {2, 0, 1, 2, 3, 5}};  // network interface
+
+void mqtt_publish(const char *message) {
+  struct mg_mqtt_opts opts = {};
+  opts.topic = mg_str(mqtt_publish_topic);
+  opts.message = mg_str(message);
+  if (mqtt_connection) mg_mqtt_pub(mqtt_connection, &opts);
+}
+
+static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+  if (ev == MG_EV_MQTT_OPEN) {
+    MG_INFO(("%lu CONNECTED to %s", c->id, MQTT_SERVER));
+    struct mg_mqtt_opts opts = {};
+    opts.topic = mg_str(mqtt_subscribe_topic);
+    mg_mqtt_sub(c, &opts);
+    MG_INFO(("%lu SUBSCRIBED to %s", c->id, mqtt_subscribe_topic));
+  } else if (ev == MG_EV_MQTT_MSG) {
+    // Received MQTT message
+    struct mg_mqtt_message *mm = (struct mg_mqtt_message *) ev_data;
+    MG_INFO(("%lu RECEIVED %.*s <- %.*s", c->id, (int) mm->data.len,
+             mm->data.ptr, (int) mm->topic.len, mm->topic.ptr));
+    exec_command(mm->data.ptr, mm->data.len);
+  } else if (ev == MG_EV_CLOSE) {
+    MG_INFO(("%lu CLOSED", c->id));
+    mqtt_connection = NULL;
+  }
+}
+
+static void timer_fn(void *arg) {
+  struct mg_mgr *mgr = (struct mg_mgr *) arg;
+  struct mg_mqtt_opts opts;
+  memset(&opts, 0, sizeof(opts));
+  opts.clean = true;
+  if (mif.state == MG_TCPIP_STATE_READY && mqtt_connection == NULL) {
+    mqtt_connection = mg_mqtt_connect(mgr, MQTT_SERVER, &opts, fn, NULL);
+  }
+  // MG_INFO(("Eth: %d, MQTT: %p", mif.state, mqtt_connection));
+}
+
+void net_init(void) {
+  // Set Mongoose logging function to a serial print
+  mg_mgr_init(&mgr);
+
+  mif.driver = &mg_tcpip_driver_w5500;
+  mif.driver_data = &spi;
+  mg_tcpip_init(&mgr, &mif);
+
+  // Start a timer that keeps MQTT connection alive
+  mg_timer_add(&mgr, 3000, MG_TIMER_REPEAT, timer_fn, &mgr);
+}
diff --git a/examples/arduino/w5500-mqtt/net.h b/examples/arduino/w5500-mqtt/net.h
new file mode 100644
index 00000000..3e6b696c
--- /dev/null
+++ b/examples/arduino/w5500-mqtt/net.h
@@ -0,0 +1,16 @@
+#pragma once
+#include "mongoose.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern struct mg_tcpip_spi spi;
+extern struct mg_mgr mgr;
+void mqtt_publish(const char *message);
+void net_init(void);
+void exec_command(const char *req, size_t req_len);
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/examples/arduino/w5500-mqtt/w5500-mqtt.ino b/examples/arduino/w5500-mqtt/w5500-mqtt.ino
index 53feecd7..1b082ca8 100644
--- a/examples/arduino/w5500-mqtt/w5500-mqtt.ino
+++ b/examples/arduino/w5500-mqtt/w5500-mqtt.ino
@@ -1,29 +1,15 @@
 #include <SPI.h>
-#include "mongoose.h"
-
-#define MQTT_SERVER "mqtt://broker.hivemq.com:1883"
-struct mg_connection *mqtt_connection;
-const char *mqtt_subscribe_topic = "mg/rx";
-const char *mqtt_publish_topic = "mg/tx";
+#include "net.h"
 
 #define SS_PIN 17   // Slave select pin
-struct mg_mgr mgr;  // Mongoose event manager
 struct mg_tcpip_spi spi = {
     NULL,                                               // SPI data
     [](void *) { digitalWrite(SS_PIN, LOW); },          // Begin transaction
     [](void *) { digitalWrite(SS_PIN, HIGH); },         // End transaction
     [](void *, uint8_t c) { return SPI.transfer(c); },  // Execute transaction
 };
-struct mg_tcpip_if mif = {.mac = {2, 0, 1, 2, 3, 5}};  // network interface
 
-static void mqtt_publish(const char *message) {
-  struct mg_mqtt_opts opts = {};
-  opts.topic = mg_str(mqtt_publish_topic);
-  opts.message = mg_str(message);
-  if (mqtt_connection) mg_mqtt_pub(mqtt_connection, &opts);
-}
-
-static void exec_command(const char *req, size_t req_len) {
+void exec_command(const char *req, size_t req_len) {
   char res[100];
   if (req_len == 2 && strncmp(req, "on", req_len) == 0) {
     digitalWrite(LED_BUILTIN, true);
@@ -50,52 +36,13 @@ static void process_input(char c) {
   }
 }
 
-static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
-  if (ev == MG_EV_MQTT_OPEN) {
-    MG_INFO(("%lu CONNECTED to %s", c->id, MQTT_SERVER));
-    struct mg_mqtt_opts opts = {};
-    opts.topic = mg_str(mqtt_subscribe_topic);
-    mg_mqtt_sub(c, &opts);
-    MG_INFO(("%lu SUBSCRIBED to %s", c->id, mqtt_subscribe_topic));
-  } else if (ev == MG_EV_MQTT_MSG) {
-    // Received MQTT message
-    struct mg_mqtt_message *mm = (struct mg_mqtt_message *) ev_data;
-    MG_INFO(("%lu RECEIVED %.*s <- %.*s", c->id, (int) mm->data.len,
-             mm->data.ptr, (int) mm->topic.len, mm->topic.ptr));
-    exec_command(mm->data.ptr, mm->data.len);
-  } else if (ev == MG_EV_CLOSE) {
-    MG_INFO(("%lu CLOSED", c->id));
-    mqtt_connection = NULL;
-  }
-}
-
-static void timer_fn(void *arg) {
-  struct mg_mgr *mgr = (struct mg_mgr *) arg;
-  struct mg_mqtt_opts opts;
-  memset(&opts, 0, sizeof(opts));
-  opts.clean = true;
-  if (mif.state == MG_TCPIP_STATE_READY && mqtt_connection == NULL) {
-    mqtt_connection = mg_mqtt_connect(mgr, MQTT_SERVER, &opts, fn, NULL);
-  }
-  MG_INFO(("Eth: %d, MQTT: %p", mif.state, mqtt_connection));
-}
-
 void setup() {
   Serial.begin(115200);
   SPI.begin();
   pinMode(SS_PIN, OUTPUT);
   pinMode(LED_BUILTIN, OUTPUT);
-
-  // Set Mongoose logging function to a serial print
   mg_log_set_fn([](char ch, void *) { Serial.print(ch); }, NULL);
-  mg_mgr_init(&mgr);
-
-  mif.driver = &mg_tcpip_driver_w5500;
-  mif.driver_data = &spi;
-  mg_tcpip_init(&mgr, &mif);
-
-  // Start a timer that keeps MQTT connection alive
-  mg_timer_add(&mgr, 3000, MG_TIMER_REPEAT, timer_fn, &mgr);
+  net_init();
 }
 
 void loop() {