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216 lines
7.3 KiB
ReStructuredText
216 lines
7.3 KiB
ReStructuredText
mDNS Service
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============
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Overview
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--------
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mDNS is a multicast UDP service that is used to provide local network service and host discovery.
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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.
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mDNS Properties
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^^^^^^^^^^^^^^^
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* ``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``
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* ``default_instance``: friendly name for your device, like ``Jhon's ESP32 Thing``. If not set, ``hostname`` will be used.
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Example method to start mDNS for the STA interface and set ``hostname`` and ``default_instance``:
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::
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mdns_server_t * mdns = NULL;
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void start_mdns_service()
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{
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//initialize mDNS service on STA interface
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esp_err_t err = mdns_init(TCPIP_ADAPTER_IF_STA, &mdns);
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if (err) {
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printf("MDNS Init failed: %d\n", err);
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return;
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}
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//set hostname
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mdns_set_hostname(mdns, "my-esp32");
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//set default instance
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mdns_set_instance(mdns, "Jhon's ESP32 Thing");
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}
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mDNS Services
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^^^^^^^^^^^^^
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mDNS can advertise information about network services that your device offers. Each service is defined by a few properties.
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* ``service``: (required) service type, prepended with underscore. Some common types can be found `here <http://www.dns-sd.org/serviceTypes.html>`_.
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* ``proto``: (required) protocol that the service runs on, prepended with underscore. Example: ``_tcp`` or ``_udp``
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* ``port``: (required) network port that the service runs on
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* ``instance``: friendly name for your service, like ``Jhon's ESP32 Web Server``. If not defined, ``default_instance`` will be used.
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* ``txt``: ``var=val`` array of strings, used to define properties for your service
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Example method to add a few services and different properties:
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::
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void add_mdns_services()
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{
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//add our services
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mdns_service_add(mdns, "_http", "_tcp", 80);
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mdns_service_add(mdns, "_arduino", "_tcp", 3232);
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mdns_service_add(mdns, "_myservice", "_udp", 1234);
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//NOTE: services must be added before their properties can be set
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//use custom instance for the web server
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mdns_service_instance_set(mdns, "_http", "_tcp", "Jhon's ESP32 Web Server");
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const char * arduTxtData[4] = {
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"board=esp32",
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"tcp_check=no",
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"ssh_upload=no",
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"auth_upload=no"
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};
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//set txt data for service (will free and replace current data)
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mdns_service_txt_set(mdns, "_arduino", "_tcp", 4, arduTxtData);
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//change service port
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mdns_service_port_set(mdns, "_myservice", "_udp", 4321);
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}
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mDNS Query
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^^^^^^^^^^
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mDNS provides methods for browsing for services and resolving host's IP/IPv6 addresses.
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Results are returned as a linked list of ``mdns_result_t`` objects. If the result is from host query,
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it will contain only ``addr`` and ``addrv6`` if found. Service queries will populate all fields
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in a result that were found.
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Example method to resolve host IPs:
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::
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void resolve_mdns_host(const char * hostname)
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{
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printf("mDNS Host Lookup: %s.local\n", hostname);
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//run search for 1000 ms
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if (mdns_query(mdns, hostname, NULL, 1000)) {
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//results were found
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const mdns_result_t * results = mdns_result_get(mdns, 0);
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//itterate through all results
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size_t i = 1;
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while(results) {
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//print result information
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printf(" %u: IP:" IPSTR ", IPv6:" IPV6STR "\n", i++
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IP2STR(&results->addr), IPV62STR(results->addrv6));
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//load next result. Will be NULL if this was the last one
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results = results->next;
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}
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//free the results from memory
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mdns_result_free(mdns);
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} else {
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//host was not found
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printf(" Host Not Found\n");
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}
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}
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Example method to resolve local services:
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::
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void find_mdns_service(const char * service, const char * proto)
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{
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printf("mDNS Service Lookup: %s.%s\n", service, proto);
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//run search for 1000 ms
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if (mdns_query(mdns, service, proto, 1000)) {
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//results were found
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const mdns_result_t * results = mdns_result_get(mdns, 0);
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//itterate through all results
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size_t i = 1;
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while(results) {
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//print result information
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printf(" %u: hostname:%s, instance:\"%s\", IP:" IPSTR ", IPv6:" IPV6STR ", port:%u, txt:%s\n", i++,
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(results->host)?results->host:"NULL", (results->instance)?results->instance:"NULL",
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IP2STR(&results->addr), IPV62STR(results->addrv6),
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results->port, (results->txt)?results->txt:"\r");
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//load next result. Will be NULL if this was the last one
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results = results->next;
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}
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//free the results from memory
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mdns_result_free(mdns);
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} else {
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//service was not found
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printf(" Service Not Found\n");
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}
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}
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Example of using the methods above:
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::
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void my_app_some_method(){
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//search for esp32-mdns.local
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resolve_mdns_host("esp32-mdns");
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//search for HTTP servers
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find_mdns_service("_http", "_tcp");
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//or file servers
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find_mdns_service("_smb", "_tcp"); //windows sharing
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find_mdns_service("_afpovertcp", "_tcp"); //apple sharing
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find_mdns_service("_nfs", "_tcp"); //NFS server
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find_mdns_service("_ftp", "_tcp"); //FTP server
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//or networked printer
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find_mdns_service("_printer", "_tcp");
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find_mdns_service("_ipp", "_tcp");
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}
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Application Example
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-------------------
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mDNS server/scanner example: `examples/protocols/mdns <https://github.com/espressif/esp-idf/tree/master/examples/protocols/mdns>`_.
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API Reference
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-------------
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Header Files
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^^^^^^^^^^^^
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* `components/mdns/include/mdns.h <https://github.com/espressif/esp-idf/blob/master/components/mdns/include/mdns.h>`_
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Macros
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^^^^^^
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Type Definitions
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^^^^^^^^^^^^^^^^
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.. doxygentypedef:: mdns_server_t
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.. doxygentypedef:: mdns_result_t
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Enumerations
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^^^^^^^^^^^^
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Structures
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^^^^^^^^^^
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.. doxygenstruct:: mdns_result_s
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:members:
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Functions
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^^^^^^^^^
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.. doxygenfunction:: mdns_init
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.. doxygenfunction:: mdns_free
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.. doxygenfunction:: mdns_set_hostname
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.. doxygenfunction:: mdns_set_instance
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.. doxygenfunction:: mdns_service_add
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.. doxygenfunction:: mdns_service_remove
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.. doxygenfunction:: mdns_service_instance_set
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.. doxygenfunction:: mdns_service_txt_set
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.. doxygenfunction:: mdns_service_port_set
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.. doxygenfunction:: mdns_service_remove_all
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.. doxygenfunction:: mdns_query
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.. doxygenfunction:: mdns_query_end
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.. doxygenfunction:: mdns_result_get_count
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.. doxygenfunction:: mdns_result_get
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.. doxygenfunction:: mdns_result_free
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