feat: Add TARGET command — runtime UDP destination config

- TARGET <ip> [port] command to change data destination live
- NVS persistence for target_ip and target_port
- Falls back to Kconfig defaults when no NVS config
- target= field added to STATUS reply
- config_save_str helper for NVS string storage

ROADMAP.md

@@ -54,7 +54,7 @@
 - [x] mDNS auto-discovery (done in v0.2)
 - [x] Watchdog + auto-recovery (done in v0.2)
 - [ ] On-device CSI processing (send metrics, not raw)
-- [ ] Configuration via UDP (WiFi SSID, target IP)
+- [x] Configuration via UDP (`TARGET <ip> [port]`, NVS persisted)
 - [ ] Comprehensive error handling
 
 ## Future

get-started/csi_recv_router/main/app_main.c

@@ -108,11 +108,18 @@ static uint8_t s_ble_own_addr_type;
 static int s_udp_socket = -1;
 static struct sockaddr_in s_dest_addr;
 static char s_udp_buffer[2048];
+static char s_target_ip[16];   /* runtime target IP (NVS or Kconfig default) */
+static uint16_t s_target_port; /* runtime target port */
 
 /* --- NVS helpers --- */
 
 static void config_load_nvs(void)
 {
+    /* Start with Kconfig defaults for target */
+    strncpy(s_target_ip, CONFIG_CSI_UDP_TARGET_IP, sizeof(s_target_ip) - 1);
+    s_target_ip[sizeof(s_target_ip) - 1] = '\0';
+    s_target_port = CONFIG_CSI_UDP_TARGET_PORT;
+
     nvs_handle_t h;
     if (nvs_open("csi_config", NVS_READONLY, &h) == ESP_OK) {
         int32_t val;
@@ -135,9 +142,16 @@ static void config_load_nvs(void)
         if (nvs_get_i8(h, "ble_scan", &ble) == ESP_OK) {
             s_ble_enabled = (ble != 0);
         }
+        size_t ip_len = sizeof(s_target_ip);
+        nvs_get_str(h, "target_ip", s_target_ip, &ip_len);
+        int32_t port;
+        if (nvs_get_i32(h, "target_port", &port) == ESP_OK && port > 0 && port <= 65535) {
+            s_target_port = (uint16_t)port;
+        }
         nvs_close(h);
-        ESP_LOGI(TAG, "NVS loaded: rate=%d tx_power=%d adaptive=%d threshold=%.6f ble=%d",
+        ESP_LOGI(TAG, "NVS loaded: rate=%d tx_power=%d adaptive=%d threshold=%.6f ble=%d target=%s:%d",
-                 s_send_frequency, s_tx_power_dbm, s_adaptive, s_motion_threshold, s_ble_enabled);
+                 s_send_frequency, s_tx_power_dbm, s_adaptive, s_motion_threshold, s_ble_enabled,
+                 s_target_ip, s_target_port);
     } else {
         ESP_LOGI(TAG, "NVS: no saved config, using defaults");
     }
@@ -165,6 +179,17 @@ static esp_err_t config_save_i8(const char *key, int8_t value)
     return err;
 }
 
+static esp_err_t config_save_str(const char *key, const char *value)
+{
+    nvs_handle_t h;
+    esp_err_t err = nvs_open("csi_config", NVS_READWRITE, &h);
+    if (err != ESP_OK) return err;
+    err = nvs_set_str(h, key, value);
+    if (err == ESP_OK) err = nvs_commit(h);
+    nvs_close(h);
+    return err;
+}
+
 /* --- LED --- */
 
 static void led_gpio_init(void)
@@ -401,11 +426,11 @@ static void udp_socket_init(void)
 
     memset(&s_dest_addr, 0, sizeof(s_dest_addr));
     s_dest_addr.sin_family = AF_INET;
-    s_dest_addr.sin_port = htons(CONFIG_CSI_UDP_TARGET_PORT);
+    s_dest_addr.sin_port = htons(s_target_port);
-    inet_pton(AF_INET, CONFIG_CSI_UDP_TARGET_IP, &s_dest_addr.sin_addr);
+    inet_pton(AF_INET, s_target_ip, &s_dest_addr.sin_addr);
 
     ESP_LOGI(TAG, "UDP socket initialized, sending to %s:%d",
-             CONFIG_CSI_UDP_TARGET_IP, CONFIG_CSI_UDP_TARGET_PORT);
+             s_target_ip, s_target_port);
 }
 
 /* --- Ping --- */
@@ -699,11 +724,11 @@ static int cmd_handle(const char *cmd, char *reply, size_t reply_size)
         }
 
         snprintf(reply, reply_size,
-                 "OK STATUS uptime=%s heap=%lu rssi=%d tx_power=%d rate=%d hostname=%s version=%s adaptive=%s motion=%d ble=%s",
+                 "OK STATUS uptime=%s heap=%lu rssi=%d tx_power=%d rate=%d hostname=%s version=%s adaptive=%s motion=%d ble=%s target=%s:%d",
                  uptime_str, (unsigned long)heap, rssi, (int)s_tx_power_dbm,
                  s_send_frequency, CONFIG_CSI_HOSTNAME, app_desc->version,
                  s_adaptive ? "on" : "off", s_motion_detected ? 1 : 0,
-                 s_ble_enabled ? "on" : "off");
+                 s_ble_enabled ? "on" : "off", s_target_ip, s_target_port);
         return strlen(reply);
     }
 
@@ -740,6 +765,38 @@ static int cmd_handle(const char *cmd, char *reply, size_t reply_size)
         return strlen(reply);
     }
 
+    /* TARGET <ip> [port] */
+    if (strncmp(cmd, "TARGET ", 7) == 0) {
+        char ip_buf[16] = {0};
+        int port = s_target_port;
+        /* parse: "TARGET 192.168.1.10" or "TARGET 192.168.1.10 5500" */
+        if (sscanf(cmd + 7, "%15s %d", ip_buf, &port) < 1) {
+            snprintf(reply, reply_size, "ERR TARGET <ip> [port]");
+            return strlen(reply);
+        }
+        /* validate IP */
+        struct in_addr test_addr;
+        if (inet_pton(AF_INET, ip_buf, &test_addr) != 1) {
+            snprintf(reply, reply_size, "ERR TARGET invalid IP");
+            return strlen(reply);
+        }
+        if (port < 1 || port > 65535) {
+            snprintf(reply, reply_size, "ERR TARGET port range 1-65535");
+            return strlen(reply);
+        }
+        strncpy(s_target_ip, ip_buf, sizeof(s_target_ip) - 1);
+        s_target_ip[sizeof(s_target_ip) - 1] = '\0';
+        s_target_port = (uint16_t)port;
+        /* update live socket destination */
+        s_dest_addr.sin_port = htons(s_target_port);
+        inet_pton(AF_INET, s_target_ip, &s_dest_addr.sin_addr);
+        /* persist */
+        config_save_str("target_ip", s_target_ip);
+        config_save_i32("target_port", (int32_t)s_target_port);
+        snprintf(reply, reply_size, "OK TARGET %s:%d", s_target_ip, s_target_port);
+        return strlen(reply);
+    }
+
     /* BLE ON/OFF */
     if (strncmp(cmd, "BLE ", 4) == 0) {
         const char *arg = cmd + 4;