move to new skeleton

tutorials/udp/sntp-time-sync/Makefile

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+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/sntp-time-sync/README.md

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+See detailed tutorial at https://mongoose.ws/tutorials/udp/sntp-time-sync/

tutorials/udp/sntp-time-sync/main.c

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+// Copyright (c) 2022 Cesanta Software Limited
+// All rights reserved
+//
+// Synchronize time with remote SNTP server
+// A working time() call is required by TLS, so an embedded device without
+// a clock that wants to use TLS, must sync time via SNTP.
+
+#include "mongoose.h"
+
+// The UNIX epoch of the boot time. Initially, we set it to 0.  But then after
+// SNTP response, we update it to the correct value, which will allow us to
+// use time(). Uptime in milliseconds is returned by mg_millis().
+static time_t s_boot_timestamp = 0;
+
+// SNTP client connection
+static struct mg_connection *s_sntp_conn = NULL;
+
+// On embedded systems, rename to time()
+time_t my_time(time_t *tp) {
+  time_t t = s_boot_timestamp + mg_millis() / 1000;
+  if (tp != NULL) *tp = t;
+  return t;
+}
+
+// SNTP client callback
+static void sfn(struct mg_connection *c, int ev, void *ev_data) {
+  if (ev == MG_EV_SNTP_TIME) {
+    int64_t t = *(int64_t *) ev_data;
+    MG_INFO(("Got SNTP time: %lld ms from epoch", t));
+    s_boot_timestamp = (time_t) ((t - mg_millis()) / 1000);
+  } else if (ev == MG_EV_CLOSE) {
+    s_sntp_conn = NULL;
+  }
+  (void) c;
+}
+
+// Called every 5 seconds. Increase that for production case.
+static void timer_fn(void *arg) {
+  struct mg_mgr *mgr = (struct mg_mgr *) arg;
+  if (s_sntp_conn == NULL) s_sntp_conn = mg_sntp_connect(mgr, NULL, sfn, NULL);
+  if (s_sntp_conn != NULL) mg_sntp_request(s_sntp_conn);
+}
+
+int main(void) {
+  struct mg_mgr mgr;        // Event manager
+  mg_mgr_init(&mgr);        // Initialise event manager
+  mg_log_set(MG_LL_DEBUG);  // Set log level
+  mg_timer_add(&mgr, 5000, MG_TIMER_REPEAT | MG_TIMER_RUN_NOW, timer_fn, &mgr);
+  for (;;) mg_mgr_poll(&mgr, 300);  // Infinite event loop
+  mg_mgr_free(&mgr);                // Free manager resources
+  return 0;
+}

tutorials/udp/sntp-time-sync/mongoose.c

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+../../../mongoose.c

tutorials/udp/sntp-time-sync/mongoose.h

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+../../../mongoose.h