Minecraft 1.7 included debugging features that show detailed information about network packets. It was a wonderful feature and we're really thankful for it. However it's not so useful anymore since it only shows packet IDs, not parameters.

It needs to be enabled by specifying a log4j2 configuration file. This can be done through the launcher for clients, or as a commandline parameter for servers, as detailed in this page. This is a vanilla feature so please don't close this ticket for that reason. Thanks.

The output in 1.7 looked like this:

[17:36:51] [Netty Client IO #1/DEBUG]:  IN: [PLAY:2] gj[message='TextComponent{text='', siblings=[TextComponent{text='<dequis> have a nice day!', siblings=[], style=Style{hasParent=true, color=null, bold=null, italic=null, underlined=null, obfuscated=null, clickEvent=null, hoverEvent=null}}], style=Style{hasParent=false, color=null, bold=null, italic=null, underlined=null, obfuscated=null, clickEvent=null, hoverEvent=null}}']

The output in 1.8 for the same kind of packet (incoming chat) looks like this:

[18:05:22] [Netty Epoll Client IO #0/DEBUG]:  IN: [PLAY:2] ja

Even packets that have no parameters used to be displayed as "xx[]", now they are just "xx"

This is a regression introduced in snapshot 14w21b. The last working released version is 1.7.10, the last working snapshot is 14w20b (one after 1.7.10). 1.8.1-pre2 is affected too.