mDNS 服务 - ESP32 - — ESP-IDF 编程指南 latest 文档

# mDNS 服务

en:[English]

## 概述

mDNS 是一种组播 UDP 服务，用来提供本地网络服务和主机发现。

绝大多数的操作系统默认都会安装 mDNS 服务，或者提供单独的安装包。`Mac OS` 默认会安装名为 `Bonjour` 的服务（该服务基于 mDNS），此外 Apple 还发布了适用于 Windows 系统的安装程序，可以在 官方支持 找到。在 `Linux` 上，mDNS 服务由 avahi 提供，通常也会被默认安装。

### mDNS 属性

> - `hostname`：设备会去响应的主机名，如果没有设置，会根据设备的网络接口名定义 `hostname` 。例如，`my-esp32` 会被解析为 `my-esp32.local`。

> - `default_instance`：默认实例名（即易记的设备名），例如 `Jhon's ESP32 Thing`。如果没有设置，将会使用 `hostname`。

以下为 STA 接口启动 mDNS 服务并设置 `hostname` 和 `default_instance` 的示例方法：

    void start_mdns_service()
    {
        // 初始化 mDNS 服务
        esp_err_t err = mdns_init();
        if (err) {
            printf("MDNS Init failed: %d\n", err);
            return;
        }

        // 设置 hostname
        mdns_hostname_set("my-esp32");
        // 设置默认实例
        mdns_instance_name_set("Jhon's ESP32 Thing");
    }

### mDNS 服务

mDNS 可以广播设备能够提供的网络服务的相关信息，每个服务会由以下属性构成。

> - `instance_name`：实例名（即易记的服务名），例如 `Jhon's ESP32 Web Server`。如果没有定义，会使用 `default_instance`。

> - `service_type`：（必需）服务类型，以下划线为前缀，这里 列出了常见的类型。

> - `proto`：（必需）服务运行所依赖的协议，以下划线为前缀，例如 `_tcp` 或者 `_udp`。

> - `port`：（必需）服务运行所用的端口号。

> - `txt`：形如 `{var, val}` 的字符串数组，用于定义服务的属性。

添加一些服务和不同属性的示例方法:

    void add_mdns_services()
    {
        // 添加服务
        mdns_service_add(NULL, "_http", "_tcp", 80, NULL, 0);
        mdns_service_add(NULL, "_arduino", "_tcp", 3232, NULL, 0);
        mdns_service_add(NULL, "_myservice", "_udp", 1234, NULL, 0);

        // 注意：必须先添加服务，然后才能设置其属性
        // web 服务器使用自定义的实例名
        mdns_service_instance_name_set("_http", "_tcp", "Jhon's ESP32 Web Server");

        mdns_txt_item_t serviceTxtData[3] = {
            {"board","esp32"},
            {"u","user"},
            {"p","password"}
        };
        // 设置服务的文本数据（会释放并替换当前数据）
        mdns_service_txt_set("_http", "_tcp", serviceTxtData, 3);

        // 修改服务端口号
        mdns_service_port_set("_myservice", "_udp", 4321);
    }

### mDNS 查询

mDNS 提供查询服务和解析主机 IP/IPv6 地址的方法。

服务查询的结果会作为 `mdns_result_t` 类型对象的链表返回。

解析主机 IP 地址的示例方法:

    void resolve_mdns_host(const char * host_name)
    {
        printf("Query A: %s.local", host_name);

        struct ip4_addr addr;
        addr.addr = 0;

        esp_err_t err = mdns_query_a(host_name, 2000,  &addr);
        if(err){
            if(err == ESP_ERR_NOT_FOUND){
                printf("Host was not found!");
                return;
            }
            printf("Query Failed");
            return;
        }

        printf(IPSTR, IP2STR(&addr));
    }

解析本地服务的示例方法:

    static const char * if_str[] = {"STA", "AP", "ETH", "MAX"};
    static const char * ip_protocol_str[] = {"V4", "V6", "MAX"};

    void mdns_print_results(mdns_result_t * results){
        mdns_result_t * r = results;
        mdns_ip_addr_t * a = NULL;
        int i = 1, t;
        while(r){
            printf("%d: Interface: %s, Type: %s\n", i++, if_str[r->tcpip_if], ip_protocol_str[r->ip_protocol]);
            if(r->instance_name){
                printf("  PTR : %s\n", r->instance_name);
            }
            if(r->hostname){
                printf("  SRV : %s.local:%u\n", r->hostname, r->port);
            }
            if(r->txt_count){
                printf("  TXT : [%u] ", r->txt_count);
                for(t=0; t<r->txt_count; t++){
                    printf("%s=%s; ", r->txt[t].key, r->txt[t].value);
                }
                printf("\n");
            }
            a = r->addr;
            while(a){
                if(a->addr.type == IPADDR_TYPE_V6){
                    printf("  AAAA: " IPV6STR "\n", IPV62STR(a->addr.u_addr.ip6));
                } else {
                    printf("  A   : " IPSTR "\n", IP2STR(&(a->addr.u_addr.ip4)));
                }
                a = a->next;
            }
            r = r->next;
        }

    }

    void find_mdns_service(const char * service_name, const char * proto)
    {
        ESP_LOGI(TAG, "Query PTR: %s.%s.local", service_name, proto);

        mdns_result_t * results = NULL;
        esp_err_t err = mdns_query_ptr(service_name, proto, 3000, 20,  &results);
        if(err){
            ESP_LOGE(TAG, "Query Failed");
            return;
        }
        if(!results){
            ESP_LOGW(TAG, "No results found!");
            return;
        }

        mdns_print_results(results);
        mdns_query_results_free(results);
    }

使用上述方法的示例:

    void my_app_some_method(){
        // 搜索 esp32-mdns.local
        resolve_mdns_host("esp32-mdns");

        // 搜索 HTTP 服务器
        find_mdns_service("_http", "_tcp");
        // 或者搜索文件服务器
        find_mdns_service("_smb", "_tcp"); // Windows 系统的共享服务
        find_mdns_service("_afpovertcp", "_tcp"); // Apple AFP 文件共享服务
        find_mdns_service("_nfs", "_tcp"); // NFS 服务器
        find_mdns_service("_ftp", "_tcp"); // FTP 服务器
        // 或者网络打印机
        find_mdns_service("_printer", "_tcp");
        find_mdns_service("_ipp", "_tcp");
    }

## 应用示例

有关 mDNS 服务器和查询器的应用示例请参考 。

## API 参考

### Header File

- include/mdns.h

### Functions

esp_err_t mdns_init(void)

  Initialize mDNS on given interface.

  返回

    - ESP_OK on success

    - ESP_ERR_INVALID_STATE when failed to register event handler

    - ESP_ERR_NO_MEM on memory error

    - ESP_FAIL when failed to start mdns task

void mdns_free(void)

  Stop and free mDNS server.

esp_err_t mdns_hostname_set(const char *hostname)

  Set the hostname for mDNS server required if you want to advertise services.

  参数

    hostname – Hostname to set

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_ARG Parameter error

    - ESP_ERR_NO_MEM memory error

esp_err_t mdns_delegate_hostname_add(const char *hostname, const mdns_ip_addr_t *address_list)

  Adds a hostname and address to be delegated A/AAAA queries will be replied for the hostname and services can be added to this host.

  参数

    - hostname – Hostname to add

    - address_list – The IP address list of the host

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_STATE mDNS is not running

    - ESP_ERR_INVALID_ARG Parameter error

    - ESP_ERR_NO_MEM memory error

esp_err_t mdns_delegate_hostname_remove(const char *hostname)

  Remove a delegated hostname All the services added to this host will also be removed.

  参数

    hostname – Hostname to remove

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_STATE mDNS is not running

    - ESP_ERR_INVALID_ARG Parameter error

    - ESP_ERR_NO_MEM memory error

bool mdns_hostname_exists(const char *hostname)

  Query whether a hostname has been added.

  参数

    hostname – Hostname to query

  返回

    - true The hostname has been added.

    - false The hostname has not been added.

esp_err_t mdns_instance_name_set(const char *instance_name)

  Set the default instance name for mDNS server.

  参数

    instance_name – Instance name to set

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_ARG Parameter error

    - ESP_ERR_NO_MEM memory error

esp_err_t mdns_service_add(const char *instance_name, const char *service_type, const char *proto, uint16_t port, mdns_txt_item_t txt[], size_t num_items)

  Add service to mDNS server.

  备注

  The value length of txt items will be automatically decided by strlen

  参数

    - instance_name – instance name to set. If NULL, global instance name or hostname will be used. Note that MDNS_MULTIPLE_INSTANCE config option needs to be enabled for adding multiple instances with the same instance type.

    - service_type – service type (_http, _ftp, etc)

    - proto – service protocol (_tcp, _udp)

    - port – service port

    - txt – string array of TXT data (eg. {{“var”,”val”},{“other”,”2”}})

    - num_items – number of items in TXT data

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_ARG Parameter error

    - ESP_ERR_NO_MEM memory error

    - ESP_FAIL failed to add service

esp_err_t mdns_service_add_for_host(const char *instance_name, const char *service_type, const char *proto, const char *hostname, uint16_t port, mdns_txt_item_t txt[], size_t num_items)

  Add service to mDNS server with a delegated hostname.

  备注

  The value length of txt items will be automatically decided by strlen

  参数

    - instance_name – instance name to set. If NULL, global instance name or hostname will be used Note that MDNS_MULTIPLE_INSTANCE config option needs to be enabled for adding multiple instances with the same instance type.

    - service_type – service type (_http, _ftp, etc)

    - proto – service protocol (_tcp, _udp)

    - hostname – service hostname. If NULL, local hostname will be used.

    - port – service port

    - txt – string array of TXT data (eg. {{“var”,”val”},{“other”,”2”}})

    - num_items – number of items in TXT data

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_ARG Parameter error

    - ESP_ERR_NO_MEM memory error

    - ESP_FAIL failed to add service

bool mdns_service_exists(const char *service_type, const char *proto, const char *hostname)

  Check whether a service has been added.

  参数

    - service_type – service type (_http, _ftp, etc)

    - proto – service protocol (_tcp, _udp)

    - hostname – service hostname. If NULL, checks for the local hostname.

  返回

    - true Correspondding service has been added.

    - false Service not found.

bool mdns_service_exists_with_instance(const char *instance, const char *service_type, const char *proto, const char *hostname)

  Check whether a service has been added.

  参数

    - instance – instance name

    - service_type – service type (_http, _ftp, etc)

    - proto – service protocol (_tcp, _udp)

    - hostname – service hostname. If NULL, checks for the local hostname.

  返回

    - true Correspondding service has been added.

    - false Service not found.

esp_err_t mdns_service_remove(const char *service_type, const char *proto)

  Remove service from mDNS server.

  参数

    - service_type – service type (_http, _ftp, etc)

    - proto – service protocol (_tcp, _udp)

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_ARG Parameter error

    - ESP_ERR_NOT_FOUND Service not found

    - ESP_ERR_NO_MEM memory error

esp_err_t mdns_service_remove_for_host(const char *instance, const char *service_type, const char *proto, const char *hostname)

  Remove service from mDNS server with hostname.

  参数

    - instance – instance name

    - service_type – service type (_http, _ftp, etc)

    - proto – service protocol (_tcp, _udp)

    - hostname – service hostname. If NULL, local hostname will be used.

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_ARG Parameter error

    - ESP_ERR_NOT_FOUND Service not found

    - ESP_ERR_NO_MEM memory error

esp_err_t mdns_service_instance_name_set(const char *service_type, const char *proto, const char *instance_name)

  Set instance name for service.

  参数

    - service_type – service type (_http, _ftp, etc)

    - proto – service protocol (_tcp, _udp)

    - instance_name – instance name to set

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_ARG Parameter error

    - ESP_ERR_NOT_FOUND Service not found

    - ESP_ERR_NO_MEM memory error

esp_err_t mdns_service_instance_name_set_for_host(const char *instance_old, const char *service_type, const char *proto, const char *hostname, const char *instance_name)

  Set instance name for service with hostname.

  参数

    - instance_old – original instance name

    - service_type – service type (_http, _ftp, etc)

    - proto – service protocol (_tcp, _udp)

    - hostname – service hostname. If NULL, local hostname will be used.

    - instance_name – instance name to set

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_ARG Parameter error

    - ESP_ERR_NOT_FOUND Service not found

    - ESP_ERR_NO_MEM memory error

esp_err_t mdns_service_port_set(const char *service_type, const char *proto, uint16_t port)

  Set service port.

  参数

    - service_type – service type (_http, _ftp, etc)

    - proto – service protocol (_tcp, _udp)

    - port – service port

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_ARG Parameter error

    - ESP_ERR_NOT_FOUND Service not found

    - ESP_ERR_NO_MEM memory error

esp_err_t mdns_service_port_set_for_host(const char *instance, const char *service_type, const char *proto, const char *hostname, uint16_t port)

  Set service port with hostname.

  参数

    - instance – instance name

    - service_type – service type (_http, _ftp, etc)

    - proto – service protocol (_tcp, _udp)

    - hostname – service hostname. If NULL, local hostname will be used.

    - port – service port

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_ARG Parameter error

    - ESP_ERR_NOT_FOUND Service not found

    - ESP_ERR_NO_MEM memory error

esp_err_t mdns_service_txt_set(const char *service_type, const char *proto, mdns_txt_item_t txt[], uint8_t num_items)

  Replace all TXT items for service.

  备注

  The value length of txt items will be automatically decided by strlen

  参数

    - service_type – service type (_http, _ftp, etc)

    - proto – service protocol (_tcp, _udp)

    - txt – array of TXT data (eg. {{“var”,”val”},{“other”,”2”}})

    - num_items – number of items in TXT data

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_ARG Parameter error

    - ESP_ERR_NOT_FOUND Service not found

    - ESP_ERR_NO_MEM memory error

esp_err_t mdns_service_txt_set_for_host(const char *instance, const char *service_type, const char *proto, const char *hostname, mdns_txt_item_t txt[], uint8_t num_items)

  Replace all TXT items for service with hostname.

  备注

  The value length of txt items will be automatically decided by strlen

  参数

    - instance – instance name

    - service_type – service type (_http, _ftp, etc)

    - proto – service protocol (_tcp, _udp)

    - hostname – service hostname. If NULL, local hostname will be used.

    - txt – array of TXT data (eg. {{“var”,”val”},{“other”,”2”}})

    - num_items – number of items in TXT data

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_ARG Parameter error

    - ESP_ERR_NOT_FOUND Service not found

    - ESP_ERR_NO_MEM memory error

esp_err_t mdns_service_txt_item_set(const char *service_type, const char *proto, const char *key, const char *value)

  Set/Add TXT item for service TXT record.

  备注

  The value length will be automatically decided by strlen

  参数

    - service_type – service type (_http, _ftp, etc)

    - proto – service protocol (_tcp, _udp)

    - key – the key that you want to add/update

    - value – the new value of the key

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_ARG Parameter error

    - ESP_ERR_NOT_FOUND Service not found

    - ESP_ERR_NO_MEM memory error

esp_err_t mdns_service_txt_item_set_with_explicit_value_len(const char *service_type, const char *proto, const char *key, const char *value, uint8_t value_len)

  Set/Add TXT item for service TXT record.

  参数

    - service_type – service type (_http, _ftp, etc)

    - proto – service protocol (_tcp, _udp)

    - key – the key that you want to add/update

    - value – the new value of the key

    - value_len – the length of the value

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_ARG Parameter error

    - ESP_ERR_NOT_FOUND Service not found

    - ESP_ERR_NO_MEM memory error

esp_err_t mdns_service_txt_item_set_for_host(const char *instance, const char *service_type, const char *proto, const char *hostname, const char *key, const char *value)

  Set/Add TXT item for service TXT record with hostname.

  备注

  The value length will be automatically decided by strlen

  参数

    - instance – instance name

    - service_type – service type (_http, _ftp, etc)

    - proto – service protocol (_tcp, _udp)

    - hostname – service hostname. If NULL, local hostname will be used.

    - key – the key that you want to add/update

    - value – the new value of the key

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_ARG Parameter error

    - ESP_ERR_NOT_FOUND Service not found

    - ESP_ERR_NO_MEM memory error

esp_err_t mdns_service_txt_item_set_for_host_with_explicit_value_len(const char *instance, const char *service_type, const char *proto, const char *hostname, const char *key, const char *value, uint8_t value_len)

  Set/Add TXT item for service TXT record with hostname and txt value length.

  参数

    - instance – instance name

    - service_type – service type (_http, _ftp, etc)

    - proto – service protocol (_tcp, _udp)

    - hostname – service hostname. If NULL, local hostname will be used.

    - key – the key that you want to add/update

    - value – the new value of the key

    - value_len – the length of the value

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_ARG Parameter error

    - ESP_ERR_NOT_FOUND Service not found

    - ESP_ERR_NO_MEM memory error

esp_err_t mdns_service_txt_item_remove(const char *service_type, const char *proto, const char *key)

  Remove TXT item for service TXT record.

  参数

    - service_type – service type (_http, _ftp, etc)

    - proto – service protocol (_tcp, _udp)

    - key – the key that you want to remove

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_ARG Parameter error

    - ESP_ERR_NOT_FOUND Service not found

    - ESP_ERR_NO_MEM memory error

esp_err_t mdns_service_txt_item_remove_for_host(const char *instance, const char *service_type, const char *proto, const char *hostname, const char *key)

  Remove TXT item for service TXT record with hostname.

  参数

    - instance – instance name

    - service_type – service type (_http, _ftp, etc)

    - proto – service protocol (_tcp, _udp)

    - hostname – service hostname. If NULL, local hostname will be used.

    - key – the key that you want to remove

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_ARG Parameter error

    - ESP_ERR_NOT_FOUND Service not found

    - ESP_ERR_NO_MEM memory error

esp_err_t mdns_service_subtype_add_for_host(const char *instance_name, const char *service_type, const char *proto, const char *hostname, const char *subtype)

  Add subtype for service.

  参数

    - instance_name – instance name. If NULL, will find the first service with the same service type and protocol.

    - service_type – service type (_http, _ftp, etc)

    - proto – service protocol (_tcp, _udp)

    - hostname – service hostname. If NULL, local hostname will be used.

    - subtype – The subtype to add.

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_ARG Parameter error

    - ESP_ERR_NOT_FOUND Service not found

    - ESP_ERR_NO_MEM memory error

esp_err_t mdns_service_remove_all(void)

  Remove and free all services from mDNS server.

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_ARG Parameter error

esp_err_t mdns_query_async_delete(mdns_search_once_t *search)

  Deletes the finished query. Call this only after the search has ended!

  参数

    search – pointer to search object

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_STATE search has not finished

    - ESP_ERR_INVALID_ARG pointer to search object is NULL

bool mdns_query_async_get_results(mdns_search_once_t *search, uint32_t timeout, mdns_result_t **results, uint8_t *num_results)

  Get results from search pointer. Results available as a pointer to the output parameter. Pointer to search object has to be deleted via `mdns_query_async_delete` once the query has finished. The results although have to be freed manually.

  参数

    - search – pointer to search object

    - timeout – time in milliseconds to wait for answers

    - results – pointer to the results of the query

    - num_results – pointer to the number of the actual result items (set to NULL to ignore this return value)

  返回

    True if search has finished before or at timeout False if search timeout is over

mdns_search_once_t *mdns_query_async_new(const char *name, const char *service_type, const char *proto, uint16_t type, uint32_t timeout, size_t max_results, mdns_query_notify_t notifier)

  Query mDNS for host or service asynchronousely. Search has to be tested for progress and deleted manually!

  参数

    - name – service instance or host name (NULL for PTR queries)

    - service_type – service type (_http, _arduino, _ftp etc.) (NULL for host queries)

    - proto – service protocol (_tcp, _udp, etc.) (NULL for host queries)

    - type – type of query (MDNS_TYPE_*)

    - timeout – time in milliseconds during which mDNS query is active

    - max_results – maximum results to be collected

    - notifier – Notification function to be called when the result is ready, can be NULL

  返回

    mdns_search_once_s pointer to new search object if query initiated successfully. NULL otherwise.

esp_err_t mdns_query_generic(const char *name, const char *service_type, const char *proto, uint16_t type, mdns_query_transmission_type_t transmission_type, uint32_t timeout, size_t max_results, mdns_result_t **results)

  Generic mDNS query All following query methods are derived from this one.

  参数

    - name – service instance or host name (NULL for PTR queries)

    - service_type – service type (_http, _arduino, _ftp etc.) (NULL for host queries)

    - proto – service protocol (_tcp, _udp, etc.) (NULL for host queries)

    - type – type of query (MDNS_TYPE_*)

    - transmission_type – either Unicast query, or Multicast query

    - timeout – time in milliseconds to wait for answers.

    - max_results – maximum results to be collected

    - results – pointer to the results of the query results must be freed using mdns_query_results_free below

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_STATE mDNS is not running

    - ESP_ERR_NO_MEM memory error

    - ESP_ERR_INVALID_ARG timeout was not given

esp_err_t mdns_query(const char *name, const char *service_type, const char *proto, uint16_t type, uint32_t timeout, size_t max_results, mdns_result_t **results)

  Query mDNS for host or service.

  Note that querying PTR types sends Multicast query, all other types send Unicast queries

  参数

    - name – service instance or host name (NULL for PTR queries)

    - service_type – service type (_http, _arduino, _ftp etc.) (NULL for host queries)

    - proto – service protocol (_tcp, _udp, etc.) (NULL for host queries)

    - type – type of query (MDNS_TYPE_*)

    - timeout – time in milliseconds to wait for answers.

    - max_results – maximum results to be collected

    - results – pointer to the results of the query results must be freed using mdns_query_results_free below

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_STATE mDNS is not running

    - ESP_ERR_NO_MEM memory error

    - ESP_ERR_INVALID_ARG timeout was not given

void mdns_query_results_free(mdns_result_t *results)

  Free query results.

  参数

    results – linked list of results to be freed

esp_err_t mdns_query_ptr(const char *service_type, const char *proto, uint32_t timeout, size_t max_results, mdns_result_t **results)

  Query mDNS for service.

  参数

    - service_type – service type (_http, _arduino, _ftp etc.)

    - proto – service protocol (_tcp, _udp, etc.)

    - timeout – time in milliseconds to wait for answer.

    - max_results – maximum results to be collected

    - results – pointer to the results of the query

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_STATE mDNS is not running

    - ESP_ERR_NO_MEM memory error

    - ESP_ERR_INVALID_ARG parameter error

esp_err_t mdns_query_srv(const char *instance_name, const char *service_type, const char *proto, uint32_t timeout, mdns_result_t **result)

  Query mDNS for SRV record.

  参数

    - instance_name – service instance name

    - service_type – service type (_http, _arduino, _ftp etc.)

    - proto – service protocol (_tcp, _udp, etc.)

    - timeout – time in milliseconds to wait for answer.

    - result – pointer to the result of the query

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_STATE mDNS is not running

    - ESP_ERR_NO_MEM memory error

    - ESP_ERR_INVALID_ARG parameter error

esp_err_t mdns_query_txt(const char *instance_name, const char *service_type, const char *proto, uint32_t timeout, mdns_result_t **result)

  Query mDNS for TXT record.

  参数

    - instance_name – service instance name

    - service_type – service type (_http, _arduino, _ftp etc.)

    - proto – service protocol (_tcp, _udp, etc.)

    - timeout – time in milliseconds to wait for answer.

    - result – pointer to the result of the query

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_STATE mDNS is not running

    - ESP_ERR_NO_MEM memory error

    - ESP_ERR_INVALID_ARG parameter error

esp_err_t mdns_query_a(const char *host_name, uint32_t timeout, esp_ip4_addr_t *addr)

  Query mDNS for A record.

  参数

    - host_name – host name to look for

    - timeout – time in milliseconds to wait for answer.

    - addr – pointer to the resulting IP4 address

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_STATE mDNS is not running

    - ESP_ERR_NO_MEM memory error

    - ESP_ERR_INVALID_ARG parameter error

esp_err_t mdns_register_netif(esp_netif_t *esp_netif)

  Register custom esp_netif with mDNS functionality mDNS service runs by default on preconfigured interfaces (STA, AP, ETH). This API enables running the service on any customized interface, either using standard WiFi or Ethernet driver or any kind of user defined driver.

  参数

    esp_netif – Pointer to esp-netif interface

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_STATE mDNS is not running or this netif is already registered

    - ESP_ERR_NO_MEM not enough memory for this in interface in the netif list (see CONFIG_MDNS_MAX_INTERFACES)

esp_err_t mdns_unregister_netif(esp_netif_t *esp_netif)

  Unregister esp-netif already registered in mDNS service.

  参数

    esp_netif – Pointer to esp-netif interface

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_STATE mDNS is not running

    - ESP_ERR_NOT_FOUND this esp-netif was not registered in mDNS service

esp_err_t mdns_netif_action(esp_netif_t *esp_netif, mdns_event_actions_t event_action)

  Set esp_netif to a desired state, or perform a desired action, such as enable/disable this interface or send announcement packets to this netif.

  - This function is used to enable (probe, resolve conflicts and announce), announce, or disable (send bye) mDNS services on the specified network interface.

  - This function must be called if users registers a specific interface using mdns_register_netif() to enable mDNS services on that interface.

  - This function could be used in IP/connection event handlers to automatically enable/announce mDNS services when network properties change and/or disable them on disconnection.

  参数

    - esp_netif – Pointer to esp-netif interface

    - event_action – Disable/Enable/Announce on this interface over IPv4/IPv6 protocol. Actions enumerated in mdns_event_actions_t type.

  返回

    - ESP_OK success

    - ESP_ERR_INVALID_STATE mDNS is not running or this netif is not registered

    - ESP_ERR_NO_MEM memory error

### Structures

struct mdns_txt_item_t

  mDNS basic text item structure Used in mdns_service_add()

  Public Members

  const char *key

    item key name

  const char *value

    item value string

struct mdns_ip_addr_s

  mDNS query linked list IP item

  Public Members

  esp_ip_addr_t addr

    IP address

  struct mdns_ip_addr_s *next

    next IP, or NULL for the last IP in the list

struct mdns_result_s

  mDNS query result structure

  Public Members

  struct mdns_result_s *next

    next result, or NULL for the last result in the list

  esp_netif_t *esp_netif

    ptr to corresponding esp-netif

  uint32_t ttl

    time to live

  mdns_ip_protocol_t ip_protocol

    ip_protocol type of the interface (v4/v6)

  char *instance_name

    instance name

  char *service_type

    service type

  char *proto

    srevice protocol

  char *hostname

    hostname

  uint16_t port

    service port

  mdns_txt_item_t *txt

    txt record

  uint8_t *txt_value_len

    array of txt value len of each record

  size_t txt_count

    number of txt items

  mdns_ip_addr_t *addr

    linked list of IP addresses found

### Macros

MDNS_TYPE_A

MDNS_TYPE_PTR

MDNS_TYPE_TXT

MDNS_TYPE_AAAA

MDNS_TYPE_SRV

MDNS_TYPE_OPT

MDNS_TYPE_NSEC

MDNS_TYPE_ANY

### Type Definitions

typedef struct mdns_search_once_s mdns_search_once_t

  Asynchronous query handle.

typedef struct mdns_ip_addr_s mdns_ip_addr_t

  mDNS query linked list IP item

typedef struct mdns_result_s mdns_result_t

  mDNS query result structure

typedef void (*mdns_query_notify_t)(mdns_search_once_t *search)

### Enumerations

enum mdns_event_actions_t

  Values:

  enumerator MDNS_EVENT_ENABLE_IP4
  enumerator MDNS_EVENT_ENABLE_IP6
  enumerator MDNS_EVENT_ANNOUNCE_IP4
  enumerator MDNS_EVENT_ANNOUNCE_IP6
  enumerator MDNS_EVENT_DISABLE_IP4
  enumerator MDNS_EVENT_DISABLE_IP6
  enumerator MDNS_EVENT_IP4_REVERSE_LOOKUP
  enumerator MDNS_EVENT_IP6_REVERSE_LOOKUP

enum mdns_ip_protocol_t

  mDNS enum to specify the ip_protocol type

  Values:

  enumerator MDNS_IP_PROTOCOL_V4
  enumerator MDNS_IP_PROTOCOL_V6
  enumerator MDNS_IP_PROTOCOL_MAX

enum mdns_query_transmission_type_t

  mDNS query type to be explicitly set to either Unicast or Multicast

  Values:

  enumerator MDNS_QUERY_UNICAST
  enumerator MDNS_QUERY_MULTICAST