Read and Write strings via ByteBuf using byte[] array

Question

I'm trying to send a string through netty with a ByteBuf. First of all I convert the string to a byte array like that:

byteBuf.writeInt(this.serverName.length());
byteBuf.writeInt(this.ipAdress.length());

byteBuf.writeBytes(this.serverName.getBytes(StandardCharsets.UTF_8));
byteBuf.writeBytes(this.ipAdress.getBytes(StandardCharsets.UTF_8));

This works well, but I don't know how to read the bytes to convert them back to the string?

I tried something like that:

int snLen = byteBuf.readInt();
int ipLen = byteBuf.readInt();

byte[] bytes = new byte[byteBuf.readableBytes()];

System.out.println(byteBuf.readBytes(bytes).readByte());
this.ipAdress = "";

There must be something to get the bytes back. You can send bytes from a string but can't get the bytes back at the end? Seems like there is a method for that, but I don't have an idea how to do that.

I hope anyone from you can help me. Thanks in advance! :)

@tima io.netty.buffer.ByteBuf.class != java.nio.ByteBuffer.class — Ferrybig
– Ferrybig, Commented Aug 19, 2017 at 8:46

Norman Maurer · Accepted Answer · 2017-08-18 18:49:41Z

3

In netty 4.1 you can use:

byteBuf.writeCharSequence(...)
byteBuf.readCharSequence(...)

answered Aug 18, 2017 at 18:49

Norman Maurer

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2 Comments

zettel Over a year ago

Thanks! Worked perfect :)

Joe Strout Over a year ago

This would be a more useful answer if it included a complete example, rather than "..." where the important bits go.

Nicholas · Accepted Answer · 2017-08-18 21:01:59Z

1

How about using Netty's own StringEncoder and StringDecoder ? http://netty.io/4.1/api/io/netty/handler/codec/string/StringEncoder.html

answered Aug 18, 2017 at 21:01

Nicholas

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Comments

panda · Accepted Answer · 2020-05-29 20:00:39Z

1

Here is an untested answer:

I assume the data order is correct.

Use this, method "readBytes(ByteBuf dst, int length)" : readBytes

Transmit side change to:

byteBuf.writeInt(this.serverName.getBytes().length);
byteBuf.writeInt(this.ipAdress.getBytes().length);

Receiving side:

int snLen = byteBuf.readInt();
int ipLen = byteBuf.readInt();

byte[] bytesServerName = new byte[snLen];
byte[] bytesIp = new byte[ipLen];

byteBuf.readBytes(bytesServerName,snLen);
byteBuf.readBytes(bytesIp, ipLen);

String serverName  = new String(bytesServerName); 
String ipAddress   = new String(bytesIp);   

System.out.println(bytesServerName);
System.out.println(bytesIp);

edited May 29, 2020 at 20:00

panda

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answered Aug 18, 2017 at 18:47

Wayne

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2 Comments

Ferrybig Over a year ago

He is writing the .length (length in chars) of the string, this isn't the same as the length in bytes, also, you never initiated the bytesServerName and the bytesIp variables

Wayne Over a year ago

Thanks, fixed those.

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