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 :: mdns_server_t * mdns = NULL; void start_mdns_service() { //initialize mDNS service on STA interface esp_err_t err = mdns_init(TCPIP_ADAPTER_IF_STA, &mdns); if (err) { printf("MDNS Init failed: %d\n", err); return; } //set hostname mdns_set_hostname(mdns, "my-esp32"); //set default instance mdns_set_instance(mdns, "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. * ``service``: (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 * ``instance``: friendly name for your service, like ``Jhon's ESP32 Web Server``. If not defined, ``default_instance`` will be used. * ``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(mdns, "_http", "_tcp", 80); mdns_service_add(mdns, "_arduino", "_tcp", 3232); mdns_service_add(mdns, "_myservice", "_udp", 1234); //NOTE: services must be added before their properties can be set //use custom instance for the web server mdns_service_instance_set(mdns, "_http", "_tcp", "Jhon's ESP32 Web Server"); const char * arduTxtData[4] = { "board=esp32", "tcp_check=no", "ssh_upload=no", "auth_upload=no" }; //set txt data for service (will free and replace current data) mdns_service_txt_set(mdns, "_arduino", "_tcp", 4, arduTxtData); //change service port mdns_service_port_set(mdns, "_myservice", "_udp", 4321); } mDNS Query ^^^^^^^^^^ mDNS provides methods for browsing for services and resolving host's IP/IPv6 addresses. Results are returned as a linked list of ``mdns_result_t`` objects. If the result is from host query, it will contain only ``addr`` and ``addrv6`` if found. Service queries will populate all fields in a result that were found. Example method to resolve host IPs:: void resolve_mdns_host(const char * hostname) { printf("mDNS Host Lookup: %s.local\n", hostname); //run search for 1000 ms if (mdns_query(mdns, hostname, NULL, 1000)) { //results were found const mdns_result_t * results = mdns_result_get(mdns, 0); //itterate through all results size_t i = 1; while(results) { //print result information printf(" %u: IP:" IPSTR ", IPv6:" IPV6STR "\n", i++ IP2STR(&results->addr), IPV62STR(results->addrv6)); //load next result. Will be NULL if this was the last one results = results->next; } //free the results from memory mdns_result_free(mdns); } else { //host was not found printf(" Host Not Found\n"); } } Example method to resolve local services:: void find_mdns_service(const char * service, const char * proto) { printf("mDNS Service Lookup: %s.%s\n", service, proto); //run search for 1000 ms if (mdns_query(mdns, service, proto, 1000)) { //results were found const mdns_result_t * results = mdns_result_get(mdns, 0); //itterate through all results size_t i = 1; while(results) { //print result information printf(" %u: hostname:%s, instance:\"%s\", IP:" IPSTR ", IPv6:" IPV6STR ", port:%u, txt:%s\n", i++, (results->host)?results->host:"NULL", (results->instance)?results->instance:"NULL", IP2STR(&results->addr), IPV62STR(results->addrv6), results->port, (results->txt)?results->txt:"\r"); //load next result. Will be NULL if this was the last one results = results->next; } //free the results from memory mdns_result_free(mdns); } else { //service was not found printf(" Service Not Found\n"); } } 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