If you are on Linux, you need additional development packages installed on your system, because you'll build the native transport.
Note that this is build-time requirement. JDK 5 (for 3.x) or 6 (for 4.0+ / 4.1+) is enough to run your Netty-based application.
Branches to look
Development of all versions takes place in each branch whose name is identical to <majorVersion>.<minorVersion>. For example, the development of 3.9 and 4.1 resides in the branch '3.9' and the branch '4.1' respectively.
Usage with JDK 9+
Netty can be used in modular JDK9+ applications as a collection of automatic modules. The module names follow the
reverse-DNS style, and are derived from subproject names rather than root packages due to historical reasons. They
are listed below:
io.netty.all
io.netty.buffer
io.netty.codec
io.netty.codec.dns
io.netty.codec.haproxy
io.netty.codec.http
io.netty.codec.http2
io.netty.codec.memcache
io.netty.codec.mqtt
io.netty.codec.redis
io.netty.codec.smtp
io.netty.codec.socks
io.netty.codec.stomp
io.netty.codec.xml
io.netty.common
io.netty.handler
io.netty.handler.proxy
io.netty.resolver
io.netty.resolver.dns
io.netty.transport
io.netty.transport.epoll (native omitted - reserved keyword in Java)
io.netty.transport.kqueue (native omitted - reserved keyword in Java)
io.netty.transport.unix.common (native omitted - reserved keyword in Java)
io.netty.transport.rxtx
io.netty.transport.sctp
io.netty.transport.udt
Automatic modules do not provide any means to declare dependencies, so you need to list each used module separately
in your module-info file.