ntp example

.github/workflows/build.yml

@@ -47,3 +47,7 @@ jobs:
       - name: Compile and test udp broadcast
         run: |
           zig build udp-broadcast
+      
+      - name: Compile and test ntp client
+        run: |
+          zig build ntp-client

build.zig

@@ -63,11 +63,18 @@ pub fn build(b: *std.build.Builder) !void {
     });
     discovery_server.addModule("network", module);
 
+    const ntp_client = b.addExecutable(.{
+        .name = "ntp_client",
+        .root_source_file = .{ .path = "examples/ntp_client.zig" },
+        .target = target,
+        .optimize = optimize,
+    });
+    ntp_client.addModule("network", module);
+
     const test_step = b.step("test", "Runs the test suite.");
     var run = b.addRunArtifact(test_runner);
 
     test_step.dependOn(&run.step);
-
 
     const sync_examples_step = b.step("sync-examples", "Builds the examples");
     sync_examples_step.dependOn(&b.addInstallArtifact(echo_example).step);
@@ -85,6 +92,9 @@ pub fn build(b: *std.build.Builder) !void {
     discovery_examples_step.dependOn(&b.addInstallArtifact(discovery_client).step);
     discovery_examples_step.dependOn(&b.addInstallArtifact(discovery_server).step);
 
+    const ntp_example_step = b.step("ntp-client", "Builds NTP client example");
+    ntp_example_step.dependOn(&b.addInstallArtifact(ntp_client).step);
+
     const all_examples_step = b.step("examples", "Builds all examples");
     all_examples_step.dependOn(&b.addInstallArtifact(echo_example).step);
     // TODO: uncomment once async is implemented
@@ -93,4 +103,5 @@ pub fn build(b: *std.build.Builder) !void {
     all_examples_step.dependOn(&b.addInstallArtifact(udp_broadcast_example).step);
     all_examples_step.dependOn(&b.addInstallArtifact(discovery_client).step);
     all_examples_step.dependOn(&b.addInstallArtifact(discovery_server).step);
+    all_examples_step.dependOn(&b.addInstallArtifact(ntp_client).step);
 }

examples/ntp_client.zig

@@ -0,0 +1,59 @@
+const std = @import("std");
+const network = @import("network");
+const debug = std.debug;
+
+pub fn main() !void {
+    try network.init();
+    defer network.deinit();
+    var request: [48]u8 = std.mem.zeroes([48]u8);
+    request[0] = 0b00100011; // NTP version 4, mode 3 (client)
+
+    var sock = try network.connectToHost(std.heap.page_allocator, "pool.ntp.org", 123, .udp);
+    defer sock.close();
+
+    try sock.writer().writeAll(&request);
+
+    var response: [48]u8 = undefined;
+    _ = try sock.reader().readAll(&response);
+
+    // The timestamp is stored in bytes 40-43 of the response
+    const seconds = @divFloor(std.time.milliTimestamp(), std.time.ms_per_s);
+
+    // zig fmt: off
+    const fractionalSeconds = @as(u64, @intCast(response[40])) << 24
+    | @as(u64, @intCast(response[41])) << 16
+    | @as(u64, @intCast(response[42])) << 8
+    | @as(u64, @intCast(response[43]));
+
+    var timestamp = @divFloor(seconds, 2_208_988_800) * std.time.ms_per_s + fractionalSeconds * (std.time.ns_per_s / 4_294_967_296);
+
+    debug.print("NTP timestamp: {}\n", .{timestamp}); //0
+
+    // result: 1970 -1 -1  0: 0: 0 (UTC 1970-01-01)
+    debug.print("{s}\n", .{try convertTimestampToTime(@as(u64, @intCast(timestamp)))});
+}
+
+pub const secs_per_day: u17 = 24 * 60 * 60;
+
+pub const EpochSeconds = struct {
+    secs: u64,
+
+    pub fn getEpochDay(self: EpochSeconds) std.time.epoch.EpochDay {
+        return .{ .day = @as(u47, @intCast(self.secs / secs_per_day)) };
+    }
+
+    pub fn getDaySeconds(self: EpochSeconds) std.time.epoch.DaySeconds {
+        return .{ .secs = std.math.comptimeMod(self.secs, secs_per_day) };
+    }
+};
+
+pub fn convertTimestampToTime(timestamp: u64) ![]const u8 {
+    const epochSeconds = EpochSeconds{ .secs = timestamp };
+    const epochDay = epochSeconds.getEpochDay();
+    const daySeconds = epochSeconds.getDaySeconds();
+    const yearDay = epochDay.calculateYearDay();
+    const monthDay = yearDay.calculateMonthDay();
+    var buf: [80:0]u8 = undefined;
+
+    return std.fmt.bufPrint(&buf, "{:04}-{:02}-{:02} {:02}:{:02}:{:02}", .{ yearDay.year, monthDay.month.numeric(), monthDay.day_index + 1, daySeconds.getHoursIntoDay(), daySeconds.getMinutesIntoHour(), daySeconds.getSecondsIntoMinute() });
+}