DataInputStream --- random incorrect parsing...

[John Thorner]

Hi,
I am working on a small java client and server program pair which at
client side packetizes data (such as jpeg image file) and appends some
header info for each packetized packet. At the server side, the
packetized data is reassembled back into the original image.

At client side I am using DataOutputStrea m/BufferedOutputS tream:

DataOutputStrea m data_out = new DataOutputStrea m(
new BufferedOutputS tream(client_so cket.getOutputS tream()));
data_out.writeI nt(seq_Num); // part
data_out.writeL ong(time_stamp) ; // of
data_out.writeI nt(image_size); // header
data_out.writeI nt(length); // for each packetized data
data_out.write( data, 0, length); // Packetized Data
On the server side I read back packetized data back sent by client and
later reassemble it back to original image:

DataInputStream data_in = new DataInputStream (
new BufferedInputSt ream(connection _socket.getInpu tStream()));

for ( ; ; ) {
seq_num = data_in.readInt ();
time = data_in.readLon g();
size = data_in.readInt ();
dlength = data_in.readInt ();
System.out.prin tln(seq_num + ", " + time + ", " + size + ", "
+ dlength);

byte[] p_data = new byte[dlength];
rlen = data_in.read(p_ data, 0, dlength);

Here's my problem
=============== ==
When I read data back at the server side I get corrupted data when I
parse byte packetized data, that is data from DataInputStream data_in

Here's the output:

seq_num=1, time=1067733150 359, size=65366, dlength=1000
Received Packet No. 1 from Node A . . .
seq_num=2, time=1067733150 361, size=65366, dlength=1000
Received Packet No. 2 from Node A . . .
seq_num=3, time=1067733150 363, size=65366, dlength=1000
Received Packet No. 3 from Node A . . .
seq_num=2134239 293, time=5009899065 144553973, size=-2132742293,
dlength=1480003 007
Exception in thread "main" java.lang.OutOf MemoryError

Any ideas what causes this error? Any help would be greatly appreciated...

-John

[Raymond DeCampo]

John Thorner wrote:

On the server side I read back packetized data back sent by client and
later reassemble it back to original image:

DataInputStream data_in = new DataInputStream (
new BufferedInputSt ream(connection _socket.getInpu tStream()));

for ( ; ; ) {
seq_num = data_in.readInt ();
time = data_in.readLon g();
size = data_in.readInt ();
dlength = data_in.readInt ();
System.out.prin tln(seq_num + ", " + time + ", " + size + ", " +
dlength);

byte[] p_data = new byte[dlength];
rlen = data_in.read(p_ data, 0, dlength);

Here's my problem
=============== ==
When I read data back at the server side I get corrupted data when I
parse byte packetized data, that is data from DataInputStream data_in

Here's the output:

seq_num=1, time=1067733150 359, size=65366, dlength=1000
Received Packet No. 1 from Node A . . .
seq_num=2, time=1067733150 361, size=65366, dlength=1000
Received Packet No. 2 from Node A . . .
seq_num=3, time=1067733150 363, size=65366, dlength=1000
Received Packet No. 3 from Node A . . .
seq_num=2134239 293, time=5009899065 144553973, size=-2132742293,
dlength=1480003 007
Exception in thread "main" java.lang.OutOf MemoryError

Any ideas what causes this error? Any help would be greatly appreciated...

The DataInputStream .read(byte[], int, int) method is not guaranteed to
read all of the bytes requested. I see from your pseudo-code above you
are saving the return value; did you also check it to make sure all of
the requested bytes were read?

Ray

[John Thorner]

Raymond DeCampo wrote:

John Thorner wrote:

On the server side I read back packetized data back sent by client and
later reassemble it back to original image:

DataInputStream data_in = new DataInputStream (
new BufferedInputSt ream(connection _socket.getInpu tStream()));

for ( ; ; ) {
seq_num = data_in.readInt ();
time = data_in.readLon g();
size = data_in.readInt ();
dlength = data_in.readInt ();
System.out.prin tln(seq_num + ", " + time + ", " + size + ", "
+ dlength);

byte[] p_data = new byte[dlength];
rlen = data_in.read(p_ data, 0, dlength);

Here's my problem
=============== ==
When I read data back at the server side I get corrupted data when I
parse byte packetized data, that is data from DataInputStream data_in

Here's the output:

seq_num=1, time=1067733150 359, size=65366, dlength=1000
Received Packet No. 1 from Node A . . .
seq_num=2, time=1067733150 361, size=65366, dlength=1000
Received Packet No. 2 from Node A . . .
seq_num=3, time=1067733150 363, size=65366, dlength=1000
Received Packet No. 3 from Node A . . .
seq_num=2134239 293, time=5009899065 144553973, size=-2132742293,
dlength=1480003 007
Exception in thread "main" java.lang.OutOf MemoryError

Any ideas what causes this error? Any help would be greatly
appreciated...

The DataInputStream .read(byte[], int, int) method is not guaranteed to
read all of the bytes requested. I see from your pseudo-code above you
are saving the return value; did you also check it to make sure all of
the requested bytes were read?

Ray

Thanks for the tip. I should have used readFully() instead. It works!!!