HTTP-NIO transport is a module of the Apache Synapse project. Apache Synapse as well as WSO2 ESB ship the HTTP-NIO transport as the default HTTP transport implementation. The two classes that implement the receiver and sender APIs are
org.apache.synapse.transport.nhttp.HttpCoreNIOSender respectively. These classes are available in the JAR file named
synapse-nhttp-transport.jar. This non-blocking transport implementation is one of the secrets behind the blistering performance figures of Apache Synapse and WSO2 ESB. The transport implementation is based on Apache HTTP Core - NIO and uses a configurable pool of non-blocking worker threads to grab incoming HTTP messages off the wire.