@Override
protected boolean handleProxyProtocol(ChannelHandlerContext ctx, Object msg) throws Exception {
    if (!authenticated) {
        authenticated = authenticate(ctx, msg);
        return false;
    }

    Socks5CommandRequest req = (Socks5CommandRequest) msg;
    assertThat(req.type(), is(Socks5CommandType.CONNECT));

    Socks5CommandResponse res =
            new DefaultSocks5CommandResponse(Socks5CommandStatus.SUCCESS, Socks5AddressType.IPv4);
    intermediaryDestination = SocketUtils.socketAddress(req.dstAddr(), req.dstPort());

    ctx.write(res);

    ctx.pipeline().remove(ENCODER);
    ctx.pipeline().remove(DECODER);

    return true;
}
 

private void onSocksSuccess(ChannelHandlerContext ctx, Socks5CommandRequest request) {
    Address serverAddr = new Address(request.dstAddr(), request.dstPort());
    createServerChannel(ctx, serverAddr).addListener(new ChannelFutureListener() {
        @Override
        public void operationComplete(ChannelFuture future) throws Exception {
            if (future.isSuccess()) {
                ConnectionInfo newConnectionInfo = new ConnectionInfo(
                        connectionInfo.getClientAddr(), serverAddr);
                ctx.writeAndFlush(new DefaultSocks5CommandResponse(
                        Socks5CommandStatus.SUCCESS,
                        request.dstAddrType(),
                        request.dstAddr(),
                        request.dstPort()));

                onServerConnected(ctx, newConnectionInfo, future.channel());
            } else {
                ctx.channel().writeAndFlush(new DefaultSocks5CommandResponse(
                        Socks5CommandStatus.FAILURE,
                        request.dstAddrType(),
                        request.dstAddr(),
                        request.dstPort()));
                ctx.close();
            }
        }
    });
}
 

@Override
protected void channelRead0(ChannelHandlerContext ctx, SocksMessage socksMessage)
        throws Exception {
    switch (socksMessage.version()) {
    case SOCKS4a:
        Socks4CommandRequest socksV4CmdRequest = (Socks4CommandRequest) socksMessage;
        if (socksV4CmdRequest.type() == Socks4CommandType.CONNECT) {
            onSocksSuccess(ctx, socksV4CmdRequest);
        } else {
            ctx.close();
        }
        break;
    case SOCKS5:
        if (socksMessage instanceof Socks5InitialRequest) {
            ctx.pipeline().addFirst(addChannelHandler(new Socks5CommandRequestDecoder()));
            ctx.writeAndFlush(new DefaultSocks5InitialResponse(Socks5AuthMethod.NO_AUTH));
        } else if (socksMessage instanceof Socks5PasswordAuthRequest) {
            ctx.pipeline().addFirst(addChannelHandler(new Socks5CommandRequestDecoder()));
            ctx.writeAndFlush(new DefaultSocks5PasswordAuthResponse(Socks5PasswordAuthStatus.SUCCESS));
        } else if (socksMessage instanceof Socks5CommandRequest) {
            Socks5CommandRequest socks5CmdRequest = (Socks5CommandRequest) socksMessage;
            if (socks5CmdRequest.type() == Socks5CommandType.CONNECT) {
                onSocksSuccess(ctx, socks5CmdRequest);
            } else {
                ctx.close();
            }
        } else {
            ctx.close();
        }
        break;
    case UNKNOWN:
        ctx.close();
        break;
    }
}
 

@Override
public void channelRead0(ChannelHandlerContext ctx, SocksMessage socksRequest) throws Exception {
    switch (socksRequest.version()) {
        case SOCKS4a:
            Socks4CommandRequest socksV4CmdRequest = (Socks4CommandRequest) socksRequest;
            if (socksV4CmdRequest.type() == Socks4CommandType.CONNECT) {
                ctx.pipeline().addLast(new SocksServerConnectHandler());
                ctx.pipeline().remove(this);
                ctx.fireChannelRead(socksRequest);
            } else {
                ctx.close();
            }
            break;
        case SOCKS5:
            if (socksRequest instanceof Socks5InitialRequest) {
                // auth support example
                //ctx.pipeline().addFirst(new Socks5PasswordAuthRequestDecoder());
                //ctx.write(new DefaultSocks5AuthMethodResponse(Socks5AuthMethod.PASSWORD));
                ctx.pipeline().addFirst(new Socks5CommandRequestDecoder());
                ctx.write(new DefaultSocks5InitialResponse(Socks5AuthMethod.NO_AUTH));
            } else if (socksRequest instanceof Socks5PasswordAuthRequest) {
                ctx.pipeline().addFirst(new Socks5CommandRequestDecoder());
                ctx.write(new DefaultSocks5PasswordAuthResponse(Socks5PasswordAuthStatus.SUCCESS));
            } else if (socksRequest instanceof Socks5CommandRequest) {
                Socks5CommandRequest socks5CmdRequest = (Socks5CommandRequest) socksRequest;
                if (socks5CmdRequest.type() == Socks5CommandType.CONNECT) {
                    ctx.pipeline().addLast(new SocksServerConnectHandler());
                    ctx.pipeline().remove(this);
                    ctx.fireChannelRead(socksRequest);
                } else {
                    ctx.close();
                }
            } else {
                ctx.close();
            }
            break;
        case UNKNOWN:
            ctx.close();
            break;
    }
}