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Difference between methods to read a byte from TCP server?

Im trying to read information sent for a client on android using the TCP protocol. In my server I have this code:
InputStream input = clienteSocket.getInputStream();
int c = input.read();
c will containt the ascci number that the client send.
I also can get this by writing:
BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
I would like to know what is the difference between both methods.

You're comparing apples and oranges here.
Your first example reads one byte from the stream, unbuffered, and returns the value of that byte. (Adding 'ASCII number' to that adds no actual information.)
Your second example sets up a buffered reader, which can read chars from the stream, buffered, but it doesn't actually read anything.
You could set up two further examples:
InputStream is = new BufferedInputStream(socket.getInputStream());
int c = is.read();
This reads a byte, with buffering.
Reader reader = new InputStreamReader(socket.getInputStream();
int c = reader.read();
This reads a char, with a little buffering: not as much as BufferedReader provides.
The realistic choices are between the two buffered versions, for efficiency reasons as outlined by #StephenC, and the choice between them is dictated by whether you want bytes or chars.

The buffered approach is better because (in most cases) reduces the number of syscalls that the JVM needs to make to the operating system. Since syscalls are relatively expensive, buffering generally gives you better performance.
In your specific example:
Each time you call c.read() on an input stream you do a syscall.
The first time you do a c.read() (or other read operation) on a buffered input stream, it reads a number of bytes into an in-memory byte-array. In second, third, etc calls to c.read(), the read will typically return a byte out of the in-memory buffer, without making a syscall.
In your example, the only case where using a buffered stream doesn't help would be if you are going to read only one byte from the socket, and then close it.
UPDATE
I didn't notice that you were comparing an unbuffered InputStream with a buffered >> Reader <<. As #EJP, points out, this is "comparing Apples and Oranges". The functionality of the two versions is different. One reades bytes and the other reads characters.
(And if you don't understand that distinction ... and why it is an important distinction ... you would be advised to read the Java Tutorial lesson on Basic I/O. Particularly the sections on byte streams, character streams and buffered streams.)

Data loss when writing bytes to a file

I'm working on a string compressor for a school assignment,
There's one bug that I can't seem to work out. The compressed data is being written a file using a FileWriter, represented by a byte array. The compression algorithm returns an input stream so the data flows as such:
piped input stream
-> input stream reader
-> data stored in char buffer
-> data written to file with file writer.
Now, the bug is, that with some very specific strings, the second to last byte in the byte array is written wrong. and it's always the same bit values "11111100".
Every time it's this bit values and always the second to last byte.
Here are some samples from the code:
InputStream compress(InputStream){
//...
//...
PipedInputStream pin = new PipedInputStream();
PipedOutputStream pout = new PipedOutputStream(pin);
ObjectOutputStream oos = new ObjectOutputStream(pout);
oos.writeObject(someobject);
oos.flush();
DataOutputStream dos = new DataOutputStream(pout);
dos.writeFloat(//);
dos.writeShort(//);
dos.write(SomeBytes); // ---Here
dos.flush();
dos.close();
return pin;
}
void write(char[] cbuf, int off, int len){
//....
//....
InputStreamReader s = new InputStreamReader(
c.compress(new ByteArrayInputStream(str.getBytes())));
s.read(charbuffer);
out.write(charbuffer);
}
A string which triggers it is "hello and good evenin" for example.
I have tried to iterate over the byte array and write them one by one, it didn't help.
It's also worth noting that when I tried to write to a file using the output stream in the algorithm itself it worked fine. This design was not my choice btw.
So I'm not really sure what i'm doing wrong here.

Considering that you're saying:
Now, the bug is, that with some very specific strings, the second to
last byte in the byte array is written wrong. and it's always the same
bit values "11111100".
You are taking a
binary stream (the compressed data)
-> reading it as chars
-> then writing it as chars.
And your are converting bytes to chars without clearly defining the encoding.
I'd say that the problem is that your InputStreamReader is translating some byte sequences in a way that you're not expecting.
Remember that in encodings like utf-8 two or three bytes may become one single char.
It can't be coincidence that the very byte pattern you pointed out (11111100) Is one of the utf-8 escape codes (1111110x). Check this wikipedia table at and you'll see that uft-8 is destructive since if a byte starts with: 1111110x the next must start with 10xxxxxx.
Meaning that if using utf-8 to convert
bytes1[] -> chars[] -> bytes2[]
in some cases bytes2 will be different from bytes1.
I recommend changing your code to remove those readers. Or specify ASCII encoding to see if that prevent the translations.

I solved this by encoding and decoding the bytes with Base64.

Java TCP/IP socket send byte-aligned data

I am having a hard time sending byte-aligned data over a socket because the examples I've been following use a PrintWriter class which converts everything to a string representation.
I want to send 3 float values, with a header and a footer. This way the consumer knows exactly how many bytes to read per transmission. My client sends something like the following:
//Add a header:
float type = params[0];
if (type == TransmitService.ACC_TYPE) out.print('a');
else if (type == TransmitService.GYR_TYPE) out.print('g');
else out.print('u'); //unknown - wtf? hasn't happened yet but just in case
//Payload:
out.print(params[1]);
out.print(params[2]);
out.print(params[3]);
//Footer:
out.print('e');
Here is the initialization of network objects:
echoSocket = new Socket(HOST, PORT);
out = new PrintWriter(echoSocket.getOutputStream(), true);
Then on the server side I want to do something like read exactly 26 bytes at a time (8 bytes per 3 floats on a 64-bit system, 1 byte for header char, 1 byte for footer char). The exact number doesn't matter, I can test and figure that out.
What's problematic is that out.print() converts everything to a string, so if I have 0.001000.. with trailing zeros, it will truncate to 0.001 as a string, which is 5 chars, giving me inconsistent byte transaction amounts for my server.
It's in MATLAB unfortunately and doing the following:
t=tcpip('0.0.0.0', 8000, 'NetworkRole', 'server');
fopen(t);
bytesToRead = 26;
data = fread(t,bytesToRead);
What should I do to consistently send my header, 3 floats, and footer to my server?
Cheers

So don't use a PrintWriter. Use a DataOutputStream. It has methods for sending floats and all other primitives.
'Byte-aligned' has nothing to do with it. All data is byte-aligned.

You shouldn't use PrintWriter, I believe.
Try using e.g. an ObjectOutputStream.
http://docs.oracle.com/javase/7/docs/api/java/io/ObjectOutputStream.html
With this one you can write bytes, chars, floats, basically
anything (including primitive types and objects).
And you don't go through a String, you write binary data.

Why does Java read random amounts from a socket but not the whole message?

I am working on a project and have a question about Java sockets. The source file which can be found here.
After successfully transmitting the file size in plain text I need to transfer binary data. (DVD .Vob files)
I have a loop such as
// Read this files size
long fileSize = Integer.parseInt(in.readLine());
// Read the block size they are going to use
int blockSize = Integer.parseInt(in.readLine());
byte[] buffer = new byte[blockSize];
// Bytes "red"
long bytesRead = 0;
int read = 0;
while(bytesRead < fileSize){
System.out.println("received " + bytesRead + " bytes" + " of " + fileSize + " bytes in file " + fileName);
read = socket.getInputStream().read(buffer);
if(read < 0){
// Should never get here since we know how many bytes there are
System.out.println("DANGER WILL ROBINSON");
break;
}
binWriter.write(buffer,0,read);
bytesRead += read;
}
I read a random number of bytes close to 99%. I am using Socket, which is TCP based,
so I shouldn't have to worry about lower layer transmission errors.
The received number changes but is always very near the end
received 7258144 bytes of 7266304 bytes in file GLADIATOR/VIDEO_TS/VTS_07_1.VOB
The app then hangs there in a blocking read. I am confounded. The server is sending the correct
file size and has a successful implementation in Ruby but I can't get the Java version to work.
Why would I read less bytes than are sent over a TCP socket?
The above is because of a bug many of you pointed out below.
BufferedReader ate 8Kb of my socket's input. The correct implementation can be found
Here

If your in is a BufferedReader then you've run into the common problem with buffering more than needed. The default buffer size of BufferedReader is 8192 characters which is approximately the difference between what you expected and what you got. So the data you are missing is inside BufferedReader's internal buffer, converted to characters (I wonder why it didn't break with some kind of conversion error).
The only workaround is to read the first lines byte-by-byte without using any buffered classes readers. Java doesn't provide an unbuffered InputStreamReader with readLine() capability as far as I know (with the exception of the deprecated DataInputStream.readLine(), as indicated in the comments below), so you have to do it yourself. I would do it by reading single bytes, putting them into a ByteArrayOutputStream until I encounter an EOL, then converting the resulting byte array into a String using the String constructor with the appropriate encoding.
Note that while you can't use a BufferedInputReader, nothing stops you from using a BufferedInputStream from the very beginning, which will make byte-by-byte reads more efficient.
Update
In fact, I am doing something like this right now, only a bit more complicated. It is an application protocol that involves exchanging some data structures that are nicely represented in XML, but they sometimes have binary data attached to them. We implemented this by having two attributes in the root XML: fragmentLength and isLastFragment. The first one indicates how much bytes of binary data follow the XML part and isLastFragment is a boolean attribute indicating the last fragment so the reading side knows that there will be no more binary data. XML is null-terminated so we don't have to deal with readLine(). The code for reading looks like this:
InputStream ins = new BufferedInputStream(socket.getInputStream());
while (!finished) {
ByteArrayOutputStream buf = new ByteArrayOutputStream();
int b;
while ((b = ins.read()) > 0) {
buf.write(b);
}
if (b == -1)
throw new EOFException("EOF while reading from socket");
// b == 0
Document xml = readXML(new ByteArrayInputStream(buf.toByteArray()));
processAnswers(xml);
Element root = xml.getDocumentElement();
if (root.hasAttribute("fragmentLength")) {
int length = DatatypeConverter.parseInt(
root.getAttribute("fragmentLength"));
boolean last = DatatypeConverter.parseBoolean(
root.getAttribute("isLastFragment"));
int read = 0;
while (read < length) {
// split incoming fragment into 4Kb blocks so we don't run
// out of memory if the client sent a really large fragment
int l = Math.min(length - read, 4096);
byte[] fragment = new byte[l];
int pos = 0;
while (pos < l) {
int c = ins.read(fragment, pos, l - pos);
if (c == -1)
throw new EOFException(
"Preliminary EOF while reading fragment");
pos += c;
read += c;
}
// process fragment
}
Using null-terminated XML for this turned out to be a really great thing as we can add additional attributes and elements without changing the transport protocol. At the transport level we also don't have to worry about handling UTF-8 because XML parser will do it for us. In your case you're probably fine with those two lines, but if you need to add more metadata later you may wish to consider null-terminated XML too.

Here is your problem. The first few lines of the program your using in.readLine() which is probably some sort of BufferedReader. BufferedReaders will read data off the socket in 8K chunks. So when you did the first readLine() it read the first 8K into the buffer. The first 8K contains your two numbers followed by newlines, then some portion of the head of the VOB file (that's the missing chunk). Now when you switched to using the getInputStream() off the socket you are 8K into the transmission assuming your starting at zero.
socket.getInputStream().read(buffer); // you can't do this without losing data.
While the BufferedReader is nice for reading character data, switching between binary and character data in a stream is not possible with it. You'll have to switch to using InputStream instead of Reader and convert the first few portions by hand to character data. If you read the file using a buffered byte array you can read the first chunk, look for your newlines and convert everything to the left of that to character data. Then write everything to the right to your file, then start reading the rest of the file.
This used to be easier with DataInputStream, but it doesn't do a good job handling character conversion for you (readLine is deprecated with BufferedReader being the only replacement - doh). Probably should write a DataInputStream replacement that under the covers uses Charset to properly handle string conversion. Then switching between characters and binary would be easier.

Your basic problem is that BufferedReader will read as much data is available and place in its buffer. It will give you the data as you ask for it. This is the whole point of buffereing i.e. to reduce the number of calls to the OS. The only safe way to use an buffered input is to use the same buffer over the life of the connection.
In your case, you only use the buffer to read two lines, however it is highly likely that 8192 bytes has been read into the buffer. (The default size of the buffer) Say the first two lines consist of 32 bytes, this leaves 8160 waiting for you to read, however you by-pass the buffer to perform the read() on the socket directly leading to 8160 bytes left in the buffer you end up discarding. (the amount you are missing)
BTW: You should be able to see this in a debugger if you inspect the contents of your buffered reader.

Sergei may have been right about data being lost inside the buffer, but I'm not sure about his explanation. (BufferedReaders don't usually hold onto data inside their buffers. He may be thinking of a problem with BufferedWriters, which can lose data if the underlying stream is shut down prematurely.) [Never mind; I had misread Sergei's answer. The rest of this is valid AFAIK.]
I think you have a problem that's specific to your application. In your client code, you start reading as follows:
public static void recv(Socket socket){
try {
BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
//...
int numFiles = Integer.parseInt(in.readLine());
... and you proceed to use in for the start of the exchange. But then you switch to using the raw socket stream:
while(bytesRead > fileSize){
read = socket.getInputStream().read(buffer);
Because in is a BufferedReader, it's already going to have filled its buffer with up to 8192 bytes from the socket input stream. Any bytes that are in that buffer, and which you don't read from in, will be lost. Your app is hanging because it believes that the server is holding onto some bytes, but the server doesn't have them.
The solution is not to do byte-by-byte reads from the socket (ouch! your poor CPU!), but to use the BufferedReader consistently. Or, to use buffering with binary data, change the BufferedReader to a BufferedInputStream that wraps the socket's InputStream.
By the way, TCP is not as reliable as many people assume it to be. For example, when the server socket closes, it's possible for it to have written data into the socket which then gets lost as the socket connection is shutdown. Calling Socket.setSoLinger can help to prevent this problem.
EDIT: Also BTW, you're playing with fire by treating byte and character data as if they're interchangeable, as you do below. If the data really is binary, then the conversion to String risks corrupting the data. Perhaps you want to be writing into a BufferedOutputStream?
// Java is retarded and reading and writing operate with
// fundamentally different types. So we write a String of
// binary data.
fileWriter.write(new String(buffer));
bytesRead += read;
EDIT 2: Clarified (or attempted to clarify :-} the handling of binary vs. String data.

Java socket listener load problem

I have made a socket listener in Java that listens on two ports for data and does operations on the listened data. Now the scenario is such that when both the listener and the device that transmits data are up and running, the listener receives data, one at a time ( each data starts with a "#S" and ends with a ".") and when the listener is not up or is not listening, the device stores the data in its local memory and as soon as the listener is up it sends all the data in the appended form like:
"#S ...DATA...[.]#S...DATA...[.]..."
Now I have implemented this in a way that, whatever data the listener gets on either port, it converts into the hex form, and then carries out operations on the hex format of the input data.The hex form of"#S" is "2353" and the hex form of "." is "2e". The code for handling the hex-converted form of the input data is as follows.
hexconverted1 is a string that contains the hex-converted form of the whole input data, that comes on any port.
String store[];
store=hexconverted1.split("2353");
for(int m=0;m<store.length;m++)
store[m]="2353"+store[m];
PrintWriter out2 = new PrintWriter(new BufferedWriter(new FileWriter("C:/Listener/array.bin", true)));
for(int iter=0;iter<store.length; iter++)
out2.println(store[iter]);
out2.close();
What I am trying to accomplish by the above code is that, whenever a bunch of data arrives, I'm trying to scan through the data and sore every single data from the bunch and store in in a string array so that the operations I wish to carry out on the hex converted form of the data can be done in an easier manner. So when I write the contents of the array to a BIN file,the output varies for the same input. When I send a bunched data of 280 data packets, appended one after the other, at times, the array contains 180, at other times 270. But for smaller bunch sizes I get the desired results and the size of the 'store' array is also as expected.
I'm pretty clueless about whats going on and any pointers would be of great help.
To make matters more lucid, the data I get on the ports are mostly unreadable and often the only readable parts are the starting bits"#S" and the end bit".". So I'm using a combination of BufferedInputStream and InputStream to read the incoming data and convert it into the hex format and I'm quite sure that the conversion to hex is coming about alright.

im using a combination of BufferedInputStream and InputStream to read the incoming data
Clutching at straws here. If you read from a Stream using both InputStream and BufferedInputStream methods, you'll get into difficulty:
InputStream is = ...
BufferedInputStream bis = new BufferedInputStream(is);
// This is OK
int b = bis.read();
...
// Reading the InputStream directly at this point is liable to
// give unpredictable results. It is likely that some bytes still
// remain in "bis"'s buffer, and a read on "is" will not return them.
int b2 = is.read();