Merge pull request #3643 from cesanta/mdns

Add SD query and response to mDNS

tutorials/udp/mdns-client/main.c

@@ -8,7 +8,8 @@ char s_theone[] = "Server.local";
 static void mdns_ev_handler(struct mg_connection *c, int ev, void *ev_data) {
   if (ev == MG_EV_MDNS_RESP) {  // is this the one ?
     struct mg_mdns_resp *resp = (struct mg_mdns_resp *) ev_data;
-    if (mg_strcasecmp(mg_str(s_theone), resp->name) == 0)
+    if (resp->rr->atype == MG_DNS_RTYPE_A &&
+        mg_strcasecmp(mg_str(s_theone), resp->name) == 0)
       MG_INFO(("%.*s is: %M", resp->name.len, resp->name.buf, mg_print_ip, &resp->addr));
   }
   (void) c;

tutorials/udp/mdns-sd-client/Makefile

@@ -0,0 +1,25 @@
+PROG ?= example                   # Program we are building
+DELETE = rm -rf                   # Command to remove files
+OUT ?= -o $(PROG)                 # Compiler argument for output file
+SOURCES = main.c mongoose.c       # Source code files
+CFLAGS = -W -Wall -Wextra -g -I.  # Build options
+
+# Mongoose build options. See https://mongoose.ws/documentation/#build-options
+CFLAGS_MONGOOSE += -DMG_ENABLE_LINES
+
+ifeq ($(OS),Windows_NT)   # Windows settings. Assume MinGW compiler. To use VC: make CC=cl CFLAGS=/MD OUT=/Feprog.exe
+  PROG ?= example.exe           # Use .exe suffix for the binary
+  CC = gcc                      # Use MinGW gcc compiler
+  CFLAGS += -lws2_32            # Link against Winsock library
+  DELETE = cmd /C del /Q /F /S  # Command prompt command to delete files
+  OUT ?= -o $(PROG)             # Build output
+endif
+
+all: $(PROG)              # Default target. Build and run program
+	$(RUN) ./$(PROG) $(ARGS)
+
+$(PROG): $(SOURCES)       # Build program from sources
+	$(CC) $(SOURCES) $(CFLAGS) $(CFLAGS_MONGOOSE) $(CFLAGS_EXTRA) $(OUT)
+
+clean:                    # Cleanup. Delete built program and all build artifacts
+	$(DELETE) $(PROG) *.o *.obj *.exe *.dSYM

tutorials/udp/mdns-sd-client/README.md

@@ -0,0 +1,43 @@
+
+Browses for `_http._tcp.local` services on the local network using mDNS/DNS-SD.
+
+```sh
+make
+cc main.c mongoose.c        -W -Wall -Wextra -g -I.   -DMG_ENABLE_LINES  -o example                                    
+./example                    
+1304aa594 3 net.c:311:mg_mgr_init       MG_IO_SIZE: 16384, TLS: none
+1304aa594 3 net.c:224:mg_listen         1 4 udp://224.0.0.251:5353
+1304aa594 3 sock.c:167:mg_send          1 4 0:0:0 34 err 0
+1304aa594 3 sock.c:361:read_conn        1 4 0:0:0 34 err 0
+1304aa594 3 dns.c:478:handle_mdns_query PTR request for _http._tcp
+1304aa5d0 3 sock.c:361:read_conn        1 4 0:0:0 289 err 0
+1304aa5d1 3 dns.c:703:handle_mdns_respo PTR response for _http._tcp.local from 3D03F3CPAU00096.local
+1304aa5d1 2 main.c:15:mdns_ev_handler   Got a response
+	SERVICE -> _http._tcp
+	NAME -> 3D03F3CPAU00096.local
+	PORT -> 80
+	TXT -> host=3D03F3CPAU00096mac=e0:50:8b:8d:2f:75ip=192.168.69.220
+	URL -> http://3D03F3CPAU00096.local:80
+
+1304aa622 3 sock.c:361:read_conn        1 4 0:0:0 226 err 0
+1304aa622 3 dns.c:703:handle_mdns_respo PTR response for _http._tcp.local from DIP-3TIR3020140717CCWR473261824.local
+1304aa622 2 main.c:15:mdns_ev_handler   Got a response
+	SERVICE -> _http._tcp
+	NAME -> DIP-3TIR3020140717CCWR473261824.local
+	PORT -> 80
+	ADDRESS -> 192.168.69.225
+	TXT -> path=/
+	URL -> http://192.168.69.225:80
+
+1304aa6f5 3 sock.c:361:read_conn        1 4 0:0:0 169 err 0
+1304aa6f5 3 dns.c:703:handle_mdns_respo PTR response for _http._tcp.local from PHILIPS_HD9255_3_6B7E5E.local
+1304aa6f5 2 main.c:15:mdns_ev_handler   Got a response
+	SERVICE -> _http._tcp
+	NAME -> PHILIPS_HD9255_3_6B7E5E.local
+	PORT -> 80
+	ADDRESS -> 192.168.69.167
+	TXT -> Device Type=Domestic Appliance
+	URL -> http://192.168.69.167:80
+
+```
+

tutorials/udp/mdns-sd-client/main.c

@@ -0,0 +1,58 @@
+// Copyright (c) 2026 Cesanta Software Limited
+// All rights reserved
+
+#include "mongoose.h"
+
+static char s_name[] = "Mongoose";
+static char s_service[] = "_http._tcp";
+
+static void mdns_ev_handler(struct mg_connection *c, int ev, void *ev_data) {
+  if (ev == MG_EV_MDNS_RESP) {
+    struct mg_mdns_resp *resp = (struct mg_mdns_resp *) ev_data;
+    if (resp->rr->atype == MG_DNS_RTYPE_PTR &&
+        mg_strcasecmp(mg_str(s_service), resp->sd.srvcproto) == 0) {
+      char addr[40];
+      MG_INFO(("Got a response"));
+      printf("\tSERVICE -> %.*s\n", (int) resp->sd.srvcproto.len,
+             resp->sd.srvcproto.buf);
+      printf("\tNAME -> %.*s\n", (int) resp->name.len, resp->name.buf);
+      if (resp->sd.port != 0)
+        printf("\tPORT -> %u\n", resp->sd.port);
+      if (resp->addr.addr.ip4 != 0) {
+        mg_snprintf(addr, sizeof(addr), "%M", mg_print_ip, &resp->addr);
+        printf("\tADDRESS -> %s\n", addr);
+      }
+      if (resp->sd.txt.buf != NULL)
+        printf("\tTXT -> %.*s\n", (int) resp->sd.txt.len, resp->sd.txt.buf);
+      if (resp->addr.addr.ip4 != 0 && resp->addr.port != 0) {
+        mg_snprintf(addr, sizeof(addr), "http://%M:%u", mg_print_ip, &resp->addr,
+                    mg_ntohs(resp->addr.port));
+        printf("\tURL -> %s\n", addr);
+      } else if (resp->sd.port != 0 && resp->name.buf != NULL) {
+        printf("\tURL -> http://%.*s:%u\n", (int) resp->name.len,
+               resp->name.buf, resp->sd.port);
+      }
+      printf("\n");
+    }
+  }
+  (void) c;
+}
+
+int main(void) {
+  struct mg_mgr mgr;
+  char query[256];
+  static struct mg_connection *c;
+  mg_log_set(MG_LL_DEBUG);  // Set log level
+  mg_mgr_init(&mgr);        // Initialise event manager
+
+  c = mg_mdns_listen(&mgr, mdns_ev_handler, s_name);  // Start mDNS server
+  if (c == NULL) return 1;
+  mg_snprintf(query, sizeof(query), "%s.local", s_service);
+   // Request service providers
+  if (!mg_mdns_query(c, query, MG_DNS_RTYPE_PTR)) return 1;
+
+  for (;;) mg_mgr_poll(&mgr, 1000);  // Event loop
+
+  mg_mgr_free(&mgr);
+  return 0;
+}

tutorials/udp/mdns-sd-client/mongoose.c

@@ -0,0 +1 @@
+../../../mongoose.c

tutorials/udp/mdns-sd-client/mongoose.h

@@ -0,0 +1 @@
+../../../mongoose.h