java - Reading 4 bytes from InputStreamReader -

i'm having issue. i'm working on simple multithread tcp server in java, , have problem:

client can send me input string, such as

[identifier] text\r\n

which okay , have done. every input query needs ended \r\n, except 1 case.

this case when client send image binary data. message has following structure:

photo[space][length of data][space][data][4 bytes of checksum in big endian]

and whole point either return a

202 okay\r\n

message when checksum matches sum of bits in data, or ...

302 bad checksum\r\n

... otherwise. however, i'm having serious issues reading 4 bytes. input source instance of inputstreamreader, acquired from:

in = new inputstreamreader(this.clientsocket.getinputstream()); 

and function inputstreamreader.read() return int of char has been read. now, tried to

            correctchecksumbytes = new byte[4];             for( int  = 0 ; < 4 ; ++i ) {                 correctchecksumbytes[i] = (byte) in.read();             }              if (correctchecksumbytes == null)   {                 throw new badsyntax();             }                         bb = bytebuffer.wrap(correctchecksumbytes);             bb.order(byteorder.big_endian);             fourbytecheck = bb.getint(); 

however, understand casting int returned in.read() wrong, since result off hige amount. lead believe usage of bytebuffer correct, dont know how fill byte array correct values.

i tried convert inputsreamreader byte array, found out it's not valid way go, since message...

photo[space][length of data][space][data][4 bytes of checksum in big endian][identifier] text\r\n

...is valid , needs interpreted 2 messages.

i did tests , found out successfuly managed read data , compute valid checksum, next 4 bytes in input 4 bytes of checksum, did not manage read yet.

also, here's example of valid photo message

photo 8 abcdefgh\x00\x00\x02\x24

so i'd ask, how can read these 4 bytes , convert them int compare computed checksum?

thanks lot

inputstreamreader read character based data. have write custom inputstream , read x bytes out of it.