1 /*
2 * Copyright 2013 The Netty Project
3 *
4 * The Netty Project licenses this file to you under the Apache License,
5 * version 2.0 (the "License"); you may not use this file except in compliance
6 * with the License. You may obtain a copy of the License at:
7 *
8 * https://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13 * License for the specific language governing permissions and limitations
14 * under the License.
15 */
16
17 package io.netty.channel;
18
19 import java.io.Serializable;
20
21 /**
22 * Represents the globally unique identifier of a {@link Channel}.
23 * <p>
24 * The identifier is generated from various sources listed in the following:
25 * <ul>
26 * <li>MAC address (EUI-48 or EUI-64) or the network adapter, preferably a globally unique one,</li>
27 * <li>the current process ID,</li>
28 * <li>{@link System#currentTimeMillis()},</li>
29 * <li>{@link System#nanoTime()},</li>
30 * <li>a random 32-bit integer, and</li>
31 * <li>a sequentially incremented 32-bit integer.</li>
32 * </ul>
33 * </p>
34 * <p>
35 * The global uniqueness of the generated identifier mostly depends on the MAC address and the current process ID,
36 * which are auto-detected at the class-loading time in best-effort manner. If all attempts to acquire them fail,
37 * a warning message is logged, and random values will be used instead. Alternatively, you can specify them manually
38 * via system properties:
39 * <ul>
40 * <li>{@code io.netty.machineId} - hexadecimal representation of 48 (or 64) bit integer,
41 * optionally separated by colon or hyphen.</li>
42 * <li>{@code io.netty.processId} - an integer between 0 and 65535</li>
43 * </ul>
44 * </p>
45 */
46 public interface ChannelId extends Serializable, Comparable<ChannelId> {
47 /**
48 * Returns the short but globally non-unique string representation of the {@link ChannelId}.
49 */
50 String asShortText();
51
52 /**
53 * Returns the long yet globally unique string representation of the {@link ChannelId}.
54 */
55 String asLongText();
56 }