Represents the globally unique identifier of a Channel.

The identifier is generated from various sources listed in the following:

• MAC address (EUI-48 or EUI-64) or the network adapter, preferably a globally unique one,
• the current process ID,
• System#currentTimeMillis(),
• System#nanoTime(),
• a random 32-bit integer, and
• a sequentially incremented 32-bit integer.

The global uniqueness of the generated identifier mostly depends on the MAC address and the current process ID, which are auto-detected at the class-loading time in best-effort manner. If all attempts to acquire them fail, a warning message is logged, and random values will be used instead. Alternatively, you can specify them manually via system properties:

• io.netty.machineId - hexadecimal representation of 48 (or 64) bit integer, optionally separated by colon or hyphen.
• io.netty.processId - an integer between 0 and 65535