Replication uses binlogs to ship changes done on the master to the slave and can be written to Binlog File and sent over the network as Binlog Network Stream.

Binlog File

Binlog files start with a Binlog File Header followed by a series of Binlog Event

Binlog File Header

A binlog file start with a ‘Binlog File Header [ 0xFE 'bin’]`

$ hexdump -C /tmp/binlog-test.log
00000000  fe 62 69 6e 19 6f c9 4c  0f 01 00 00 00 66 00 00  |.bin.o.L.....f..|
00000010  00 6a 00 00 00 00 00 04  00 6d 79 73 71 6c 2d 70  |.j.......mysql-p|
00000020  72 6f 78 79 2d 30 2e 37  2e 30 00 00 00 00 00 00  |roxy-0.7.0......|
...

Binlog Network Stream

Network streams are requested with COM_BINLOG_DUMP and prepend each Binlog Event with 00 OK-byte.

Binlog Version

Depending on the MySQL version that created the binlog the format is slightly different. Four versions are currently known:

Binlog version	MySQL Version
1	MySQL 3.23 - < 4.0.0
2	MySQL 4.0.0 - 4.0.1
3	MySQL 4.0.2 - < 5.0.0
4	MySQL 5.0.0+

Version 1

Supported Statement Based Replication Events

Version 2

Can be ignored as it was only used in early alpha versinos of MySQL 4.1 and won't be documented here.

Version 3

Added the relay logs and changed the meaning of the log position

Version 4

Added the FORMAT_DESCRIPTION_EVENT and made the protocol extensible.

In MySQL 5.1.x the Row Based Replication Events were added.