189 lines
6.3 KiB
ReStructuredText
189 lines
6.3 KiB
ReStructuredText
mDNS Service
|
|
============
|
|
|
|
Overview
|
|
--------
|
|
|
|
mDNS is a multicast UDP service that is used to provide local network service and host discovery.
|
|
|
|
mDNS is installed by default on most operating systems or is available as separate package. On ``Mac OS`` it is installed by default and is called ``Bonjour``. Apple releases an installer for ``Windows`` that can be found `on Apple's support page <https://support.apple.com/downloads/bonjour%2520for%2520windows>`_. On ``Linux``, mDNS is provided by `avahi <https://github.com/lathiat/avahi>`_ and is usually installed by default.
|
|
|
|
mDNS Properties
|
|
^^^^^^^^^^^^^^^
|
|
|
|
* ``hostname``: the hostname that the device will respond to. If not set, the ``hostname`` will be read from the interface. Example: ``my-esp32`` will resolve to ``my-esp32.local``
|
|
* ``default_instance``: friendly name for your device, like ``Jhon's ESP32 Thing``. If not set, ``hostname`` will be used.
|
|
|
|
Example method to start mDNS for the STA interface and set ``hostname`` and ``default_instance``:
|
|
|
|
.. highlight:: c
|
|
|
|
::
|
|
|
|
void start_mdns_service()
|
|
{
|
|
//initialize mDNS service
|
|
esp_err_t err = mdns_init();
|
|
if (err) {
|
|
printf("MDNS Init failed: %d\n", err);
|
|
return;
|
|
}
|
|
|
|
//set hostname
|
|
mdns_hostname_set("my-esp32");
|
|
//set default instance
|
|
mdns_instance_name_set("Jhon's ESP32 Thing");
|
|
}
|
|
|
|
mDNS Services
|
|
^^^^^^^^^^^^^
|
|
|
|
mDNS can advertise information about network services that your device offers. Each service is defined by a few properties.
|
|
|
|
* ``instance_name``: friendly name for your service, like ``Jhon's ESP32 Web Server``. If not defined, ``default_instance`` will be used.
|
|
* ``service_type``: (required) service type, prepended with underscore. Some common types can be found `here <http://www.dns-sd.org/serviceTypes.html>`_.
|
|
* ``proto``: (required) protocol that the service runs on, prepended with underscore. Example: ``_tcp`` or ``_udp``
|
|
* ``port``: (required) network port that the service runs on
|
|
* ``txt``: ``{var, val}`` array of strings, used to define properties for your service
|
|
|
|
Example method to add a few services and different properties::
|
|
|
|
void add_mdns_services()
|
|
{
|
|
//add our services
|
|
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);
|
|
|
|
//NOTE: services must be added before their properties can be set
|
|
//use custom instance for the web server
|
|
mdns_service_instance_name_set("_http", "_tcp", "Jhon's ESP32 Web Server");
|
|
|
|
mdns_txt_item_t serviceTxtData[3] = {
|
|
{"board","esp32"},
|
|
{"u","user"},
|
|
{"p","password"}
|
|
};
|
|
//set txt data for service (will free and replace current data)
|
|
mdns_service_txt_set("_http", "_tcp", serviceTxtData, 3);
|
|
|
|
//change service port
|
|
mdns_service_port_set("_myservice", "_udp", 4321);
|
|
}
|
|
|
|
mDNS Query
|
|
^^^^^^^^^^
|
|
|
|
mDNS provides methods for browsing for services and resolving host's IP/IPv6 addresses.
|
|
|
|
Results for services are returned as a linked list of ``mdns_result_t`` objects.
|
|
|
|
Example method to resolve host IPs::
|
|
|
|
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));
|
|
}
|
|
|
|
Example method to resolve local services::
|
|
|
|
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 == MDNS_IP_PROTOCOL_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);
|
|
}
|
|
|
|
Example of using the methods above::
|
|
|
|
void my_app_some_method(){
|
|
//search for esp32-mdns.local
|
|
resolve_mdns_host("esp32-mdns");
|
|
|
|
//search for HTTP servers
|
|
find_mdns_service("_http", "_tcp");
|
|
//or file servers
|
|
find_mdns_service("_smb", "_tcp"); //windows sharing
|
|
find_mdns_service("_afpovertcp", "_tcp"); //apple sharing
|
|
find_mdns_service("_nfs", "_tcp"); //NFS server
|
|
find_mdns_service("_ftp", "_tcp"); //FTP server
|
|
//or networked printer
|
|
find_mdns_service("_printer", "_tcp");
|
|
find_mdns_service("_ipp", "_tcp");
|
|
}
|
|
|
|
Application Example
|
|
-------------------
|
|
|
|
mDNS server/scanner example: :example:`protocols/mdns`.
|
|
|
|
API Reference
|
|
-------------
|
|
|
|
.. include:: /_build/inc/mdns.inc
|
|
|
|
|