ReadServer 参考自：https://medium.com/learning-the-go-programming-language/lets-make-an-ntp-client-in-go-287c4b9a969f
(server string)
| 143 | |
| 144 | // ReadServer 参考自：https://medium.com/learning-the-go-programming-language/lets-make-an-ntp-client-in-go-287c4b9a969f |
| 145 | func (this *ClockManager) ReadServer(server string) (time.Time, error) { |
| 146 | conn, err := net.Dial("udp", server+":123") |
| 147 | if err != nil { |
| 148 | return time.Time{}, fmt.Errorf("connect to server failed: %w", err) |
| 149 | } |
| 150 | defer func() { |
| 151 | _ = conn.Close() |
| 152 | }() |
| 153 | err = conn.SetDeadline(time.Now().Add(5 * time.Second)) |
| 154 | if err != nil { |
| 155 | return time.Time{}, err |
| 156 | } |
| 157 | |
| 158 | // configure request settings by specifying the first byte as |
| 159 | // 00 011 011 (or 0x1B) |
| 160 | // | | +-- client mode (3) |
| 161 | // | + ----- version (3) |
| 162 | // + -------- leap year indicator, 0 no warning |
| 163 | |
| 164 | var req = &NTPPacket{Settings: 0x1B} |
| 165 | err = binary.Write(conn, binary.BigEndian, req) |
| 166 | if err != nil { |
| 167 | return time.Time{}, fmt.Errorf("write request failed: %w", err) |
| 168 | } |
| 169 | |
| 170 | var resp = &NTPPacket{} |
| 171 | err = binary.Read(conn, binary.BigEndian, resp) |
| 172 | if err != nil { |
| 173 | return time.Time{}, fmt.Errorf("write server response failed: %w", err) |
| 174 | } |
| 175 | |
| 176 | const ntpEpochOffset = 2208988800 |
| 177 | |
| 178 | var secs = float64(resp.TxTimeSec) - ntpEpochOffset |
| 179 | var nanos = (int64(resp.TxTimeFrac) * 1e9) >> 32 |
| 180 | return time.Unix(int64(secs), nanos), nil |
| 181 | } |