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Unable to read data from InputStream

I'm trying to learn java socket programming, but I have a trouble with the read function of InputStream.
At first, I created a socket to connect to the server. After the connection is established, the server then send back the message that "the connection is established" and the read function is work fine. Then I tried to send byte message to the server, but I can't read the data from the InputStream because my program is stuck at "in.read(buf)" line. Could anyone point me out how can I solve this issue.
Socket client = new Socket("xxx.xxx.xxx.xxx", 45000);
InputStream in = client.getInputStream();
OutputStream out = client.getOutputStream();
for (int i = 0; i < 5; i++) {
byte[] buf = new byte[1024];
int data_size = in.read(buf);
String msg = "";
for (int j = 0; j < data_size; j++) {
msg += String.valueOf((char) buf[i]);
}
System.out.println(msg);
out.write(65);
out.flush();
}

InputStream.read() is a blocking call. Given the code you have provided, you are reading from the socket before writing to the socket so you will block on the first read forever. Or at least until the timeout.

#Peter Could be right. Also, closing the streams after their usage might help avoiding unexpected issues.

input.read() never returns -1

I am writing a proxy server in Java.
Initially, I do (simplified)
server = new ServerSocket(5568);
incoming = server.accept();
input = incoming.getInputStream();
...
outgoing = new Socket(host, 80);
output = outgoing.getOutputStream();
output.write(inputbuffer, 0, i);
where inputbuffer is some collection of bytes received so far (I read the incoming data up until the part where I know the host header, and then open a connection to the server and send what I have so far). So server is my welcome socket, input is the data coming to my proxy from the client, and output is the data to the serve from my proxy.
Next, I want the output from the server to be written to the client in parallel with the client still possibly writing stuff to the server. So I create a separate thread to read from the client:
final InputStream finalInput = input;
final OutputStream finalOutput = output;
Thread sendingStuff = new Thread(){
public void run(){
int c;
while ((c = finalInput.read()) != -1){
finalOutput.write((byte)c);
finalOutput.flush();
}
finalInput.close();
finalOutput.close();
}
}
sendingStuff.start();
Finally, I have a different section in the main thread to read from the server and write that to the client.
InputStream reverseInput = outgoing.getInputStream();
OutputStream reverseOutput = incoming.getOutputStream();
int c;
while ((c = reverseInput.read()) != -1){
reverseOutput.write((byte)c);
reverseOutput.flush();
}
reverseInput.close();
reverseOutput.close();
What happens is I get input, and send output, but the browser spins forever and the line in the thread that's reading from the client never gets a -1 signal.
A lot of the time I get errors that say things like "invalid header name" or "your browser sent a request that the server could not understand" and I think it has to do with this problem I'm having. One time I even got an IOException: Socket Closed on the line that reads from the client.
So why isn't the client sending an EOF? And is this the right way to go about doing this?

"I think it's because my HTTP request has Connection: keep-alive. How do I handle this?"
I think maybe you can just open your socket once for one connection.
Try to have flag like isNewConnection. set it to true at first and after the connection is initiated, set it to false.

C++ Client and Java Server

I did a Java Socket server, and a C++ Client.
However, the client connects to the server, without problems.
But when I write something client-server, the server doesn't catch the message.
What I'm doing wrong?
A little bit of the code of the Java Server:
DataInputStream dis=new DataInputStream(usrSocket.getInputStream());
ByteArrayOutputStream out = new ByteArrayOutputStream();
int data;
while((data = dis.read())>=0) {
out.write(data);
}
byte[] bytes = out.toByteArray();
String decrypt = new String(bytes);
if(decrypt.equals("status")){
System.out.println("Status emitted.");
}
System.out.println("Received a message.");
C++ Client writing:
QByteArray qba;
qba.append(text);
sock->write(qba.data());
qDebug() << "Send status";
I need help with that, thank you very much.
(that variable "text" it's a QString)
EDIT
Java server: That's only one part of all the code, the main thread waits for connections (Socket sock = server.accept()) and create a new thread for each user.
The code that I published of the java server, its one part of that threads for the users.
If you need ALL the code, plese tell me.
I will be waiting the answers!
Thank u very much!
Sorry if I answer ya late.

Try this code for Java Server.
ServerSocket ss = new ServerSocket(Port_No);
Socket incomingClient = ss.accept();
InputStream i = incomingClient.getInputStream();
OutputStream o = incomingClient.getOutputStream(); // Use it write to the Client Socket
InputStreamReader isr = new InputStreamReader(i);
BufferedReader br = new BufferedReader(isr);
String str = new String();
while ((str = br.readLine())!=null){
// do what you want with the data received in str.
}

As youre using QTcpSocket, it highly likely that you are running the client in the default asynchronous mode. This means after when you write after calling connectToHost, nothing will be sent as the socket is not connected.
Try using:
socket->connectToHost(hostAddress, hostPort, QIODevice::ReadWrite);
if (socket->waitForConnected()) {
QString text = "test string";
QByteArray array;
array.append(string);
qDebug() << socket->write(array);
} else {
// connect error!
}

Your Java code reads the socket until EOS and then prints something, which by the way is not a decryption operation. Your C++ client writes something and never closes the socket. So the server can never get out of the read loop.

If I read it correctly it is caused by the fact that your client is still running. Read() returns number >= 0 until the client socket is closed.

Read data from inputstream without client side "flush()"

I have implemented a Java program that reads data from GPS Devices through ServerSocket.
ServerSocket serverSocket = new ServerSocket(13811);
serverSocket.setReceiveBufferSize(receiveBufferSize);
Socket incomingSocket = serverSocket.accept();
InputStream stream = incomingSocket.getInputStream();
byte[] buffer = new byte[1000];
StringBuffer sb = new StringBuffer();
System.out.println("START getting message from TCP stream: " + dateFormat.format(Calendar.getInstance().getTime()));
while (stream.read(buffer) > 0)
{
sb.append(new String(buffer));
System.out.println(sb.toString());
}
System.out.println("[incomingMessage]: " + incomingMessage);
System.out.println("FINISHED getting message from TCP stream: " + dateFormat.format(Calendar.getInstance().getTime()));
However, we found out that there was large delay (i.e. large deviation between Sys out "START..." and "FINISHED..." time above). The time was spent on inputStream.read().
If I use a Java client to connect to the above server port and send data to it, the message is readable by server's inputStream within a few ms. Below shows the Java client code.
Socket socket = new Socket("localhost", 13811);
DataOutputStream out = new DataOutputStream(new BufferedOutputStream(socket.getOutputStream()));
String tobesend = "testing message 1";
out.writeBytes(tobesend);
out.flush();
out.close();
However, if I add a "Thread.Sleep(10*1000)" before "out.flush()" and "out.close()", the delay at Server side will become 10seconds... Therefore I suspect if the GPS Device did not perform the "flush" and resulting the delay of inputstream.read() at server side...
Unfortunately, we have no control on the GPS Device TCP calls so I can't make any modifications on it to enforce it to "flush" message to my inputstream... Please advice if there is any means that server side can read data from inputstream without such delay even the client side (i.e. the GPS device) do not perform a "flush"?

The receiver cannot read data which has not been sent. It cannot force the other end to send data which has not been sent either.

Thanks for Peter Lawrey's advice and we used TCPDump to proved that the data are flushed to our server a few seconds after they establish the connection. That's why the server program captured the large delay.
But then, we perform some load test with the same Server program by having 4000 testing GPS devices pushing data to it every 5mins, each data is around 300bytes.
We tried to modify the server code by introducing Threadpool to handle the TCP data retrieval and hope that would give us better performance.
We have turned on TCPDump, and found that this time the time deviation was found between the TCPDump timestamp and the "START..." timestamp captured in the Java program. The deviation was around several seconds to less than 20 seconds...
Any suggestion on how to troubleshoot the issue?
Initialization of Threadpool:
blockingQueueForRetriveTCPMsg = new LinkedBlockingQueue<Runnable>(50);
threadPoolExecutorForRetriveTCPMsg = new ThreadPoolExecutor(
50,1200, 0, TimeUnit.SECONDS,
blockingQueueForRetriveTCPMsg,
new ThreadPoolExecutor.CallerRunsPolicy());
ServerSocket.accept() :
ServerSocket serverSocket = new ServerSocket(13811);
serverSocket.setReceiveBufferSize(receiveBufferSize);
Socket incomingSocket = serverSocket.accept();
RetrieveTcpMessage retrieveTcpMessage = new RetrieveTcpMessage(incomingSocket);
Thread retrieveTcpMessageThread = new Thread(retrieveTcpMessage);
threadPoolExecutorForRetriveTCPMsg.execute(retrieveTcpMessageThread);
Inside RetrieveTcpMessage.run(), simuilar to before:
InputStream stream = incomingSocket.getInputStream();
byte[] buffer = new byte[1000];
StringBuffer sb = new StringBuffer();
System.out.println("START getting message from TCP stream: " + dateFormat.format(Calendar.getInstance().getTime()));
while (stream.read(buffer) > 0)
{
sb.append(new String(buffer));
System.out.println(sb.toString());
}
System.out.println("[incomingMessage]: " + incomingMessage);
System.out.println("FINISHED getting message from TCP stream: " + dateFormat.format(Calendar.getInstance().getTime()));

Process raw HTTP headers by HttpClient in Java

My client receive raw HTTP headers (including GET, POST, Multipart POST, etc.) and I want to send them to a server and get output.
But I don't want to parse whole request manually, then set all that parsed stuff to HttpClient...
Does an elegant way to do this (even something like code below)?
AGoodHttpClient response = new AGoodHttpClient(host, port, myHeaders);
InputStream in = response.getInputStream();
// ...
Edited
Let's say I have this code. How do I recognize EOS (-1 isn't working for HTTP/1.1). Is there a guaranteed way how to cut the connection, when transfer is done? I want something what will care about cutting a connection (something like HttpClient), but with direct access to sending headers (like outToServer.write(myHeaders)).
Socket connectionToServer = new Socket(host, port);
OutputStream outToServer = connectionToServer.getOutputStream();
outToServer.write(myHeaders.getBytes());
InputStream inputFromServer = connectionToServer.getInputStream();
byte[] buff = new byte[1024];
int count;
while ((count = inputFromServer.read(buff)) != -1) {
System.out.write(buff, 0, count);
}
Thanks for help!