Java tutorial
/* * Copyright 2014 The Netty Project * * The Netty Project licenses this file to you under the Apache License, * version 2.0 (the "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at: * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the * License for the specific language governing permissions and limitations * under the License. */ package io.netty.handler.codec.socksx.v5; import io.netty.buffer.ByteBuf; import io.netty.channel.ChannelHandlerContext; import io.netty.handler.codec.DecoderException; import io.netty.handler.codec.DecoderResult; import io.netty.handler.codec.ReplayingDecoder; import io.netty.handler.codec.socksx.SocksVersion; import io.netty.handler.codec.socksx.v5.Socks5CommandRequestDecoder.State; import io.netty.util.internal.ObjectUtil; import java.util.List; /** * Decodes a single {@link Socks5CommandRequest} from the inbound {@link ByteBuf}s. * On successful decode, this decoder will forward the received data to the next handler, so that * other handler can remove or replace this decoder later. On failed decode, this decoder will * discard the received data, so that other handler closes the connection later. */ public class Socks5CommandRequestDecoder extends ReplayingDecoder<State> { enum State { INIT, SUCCESS, FAILURE } private final Socks5AddressDecoder addressDecoder; public Socks5CommandRequestDecoder() { this(Socks5AddressDecoder.DEFAULT); } public Socks5CommandRequestDecoder(Socks5AddressDecoder addressDecoder) { super(State.INIT); this.addressDecoder = ObjectUtil.checkNotNull(addressDecoder, "addressDecoder"); } @Override protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception { try { switch (state()) { case INIT: { final byte version = in.readByte(); if (version != SocksVersion.SOCKS5.byteValue()) { throw new DecoderException("unsupported version: " + version + " (expected: " + SocksVersion.SOCKS5.byteValue() + ')'); } final Socks5CommandType type = Socks5CommandType.valueOf(in.readByte()); in.skipBytes(1); // RSV final Socks5AddressType dstAddrType = Socks5AddressType.valueOf(in.readByte()); final String dstAddr = addressDecoder.decodeAddress(dstAddrType, in); final int dstPort = in.readUnsignedShort(); out.add(new DefaultSocks5CommandRequest(type, dstAddrType, dstAddr, dstPort)); checkpoint(State.SUCCESS); } case SUCCESS: { int readableBytes = actualReadableBytes(); if (readableBytes > 0) { out.add(in.readRetainedSlice(readableBytes)); } break; } case FAILURE: { in.skipBytes(actualReadableBytes()); break; } } } catch (Exception e) { fail(out, e); } } private void fail(List<Object> out, Exception cause) { if (!(cause instanceof DecoderException)) { cause = new DecoderException(cause); } checkpoint(State.FAILURE); Socks5Message m = new DefaultSocks5CommandRequest(Socks5CommandType.CONNECT, Socks5AddressType.IPv4, "0.0.0.0", 1); m.setDecoderResult(DecoderResult.failure(cause)); out.add(m); } }