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why inputstream can not recieve a message before the outputstream close in TCP [duplicate]

This question already has answers here:
Writing messages to client socket using DataOutputStream to Server Socket only sent after closing the Client Socket why?
(2 answers)
Closed 5 years ago.
I use code like this in my client
DataOutputStream out = new DataOutputStream(client.getOutputStream());
out.writeUTF(mssage);
out.flush();
while(true){
}
with this code in my server
DataInputStream in=new DataInputStream( c1.getInputStream()) ;
System.out.println(in.readUTF());
it works.
However, if I use this following code in my client
OutputStream out=client.getOutputStream();
out.write(mssage.getBytes());
out.flush();
while(true){
}
and this code in my server
InputStream in= c1.getInputStream();
byte [] b=new byte [32];
while((in.read(b))!=-1){
toprint+=new String (b);
}
System.out.print(toprint);
the server can not receive the massage until i close the client or close the outputstream,and there will a connection reset error.
What's the reason?

Your server is reading its input stream until end of stream before it prints anything, and end of stream on a socket doesn't occur until the peer closes the socket or shuts it down for output.
The other problem is that your read loop isn't correct, as it ignores the read count.
Try this:
int count;
while ((count = in.read(b)) != -1){
toprint+=new String (b, 0, count);
System.out.write(b, 0, count);
}

TCP Video file transfer

I'm trying to make a video file transfer but am having problems getting the server to start sending bytes.
The first step is for the client to connect, the socket gets accepted. Then the client sends the video file name but the server never reads this.
This is the code for the server up until it blocks:
try(ServerSocket serverSocket = new ServerSocket(4005))
{
Socket socket = serverSocket.accept();
System.out.println("accepted");
OutputStream os = socket.getOutputStream();
BufferedReader receiveReader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
System.out.println("This gets printed");
String request = receiveReader.readLine();//never passes this line
System.out.println("This doesn't get printed");
and this is the client up until it blocks waiting for the server to send the video bytes:
try(Socket socket = new Socket(IPAddress, 4005))
{
byte[] messageBytes = new byte[10000];
DataOutputStream outputStream = new DataOutputStream(socket.getOutputStream());
outputStream.writeBytes("REQUEST;"+videoPath);//This is the line that should send the bytes for the server to read, so it won't block.
String home = System.getProperty("user.home");
String path = home+"\\Downloads" + videoName;
path = path.trim();
FileOutputStream fos = new FileOutputStream(path);
BufferedOutputStream bos = new BufferedOutputStream(fos);
InputStream is = socket.getInputStream();
int bytesRead = 0;
System.out.println("Downloading file...");
while((bytesRead = is.read(messageBytes))!=-1)//This blocks here
Why on earth isn't the server reading the "Request" + videoPath bytes that the server is sending? I tried outputStream.flush() as well, no luck.

Usual problem. You're reading a line but you aren't writing a line. Add a line terminator to the sent message.
When you fix this you will then discover that you can't mix buffered streams and readers on the same socket. I suggest you do all the I/O via the DataInput/OutputStream classes, using read/writeUTF() for the name.
If you're sending multiple files see my answer there.

Why does order of instantiation seem to matter for input and output streams in Java?

I have the following code that works (please assume that hostname and port are initialized to their proper values, and that Message is a serializable class):
//Example 1 - everything works as expected
Message message = new Message();
try(Socket serverSocket = new Socket(hostname, port))
{
ObjectOutputStream outStream = new ObjectOutputStream(serverSocket.getOutputStream());
outStream.writeObject(message);
outStream.flush();
ObjectInputStream inStream = new ObjectInputStream(serverSocket.getInputStream());
Object response = inStream.readObject();
}
When I move the instantiation of the ObjectInputStream to occur immediately after the ObjectOutputStream instantiation, execution of my application hangs indefinitely:
//Example 2 - client locks up
Message message = new Message();
try(Socket serverSocket = new Socket(hostname, port))
{
ObjectOutputStream outStream = new ObjectOutputStream(serverSocket.getOutputStream());
ObjectInputStream inStream = new ObjectInputStream(serverSocket.getInputStream());
outStream.writeObject(message);
outStream.flush();
Object response = inStream.readObject();
}
I'm looking for a good explanation as to why the second example locks up consistently, and the first example seems to work without a hitch. Strangely, if I use a debugger (Eclipse debugger) on the client and server with this second example, I'm seeing the message make it through to the server, so the writeObject() call is being executed. However, in the client, the debugger gets stuck on the constructor for the ObjectInputStream.

If we go and have a read of the API docs for the ObjectInputStream constructor
The important part:
This constructor will block until the corresponding ObjectOutputStream
has written and flushed the header.

Constructing an ObjectOutputStream writes a header to the stream. Constructing an ObjectInputStream reads it. If both ends construct the ObjectInputStream first, you will therefore get a deadlock.
Solution: construct the ObjectOutputStream first, at both ends, to make sure it can't happen.

Java socket programming writebytes to readline

I am trying to get a java server and client communicating. For streaming data to the server I have this code:
Socket ClientSocket = null;
ClientSocket = new Socket(IPAddress, portInt);
DataOutputStream outToClient = new DataOutputStream(ClientSocket.getOutputStream());
outToClient.writeBytes(command);
outToClient.flush();
And for the server I have:
ServerSocket mysocket = new ServerSocket(8081);
Socket connectionsocket = mysocket.accept();
BufferedReader inFromClient =
new BufferedReader(new InputStreamReader(connectionsocket.getInputStream()));
DataOutputStream outToClient = new DataOutputStream(connectionsocket.getOutputStream());
//program hangs here, client not sending
GetRequest = inFromClient.readLine();
System.out.println("Received: " + GetRequest);
These are only short portions of the overall code, I have found that the program hangs on the server side when the readLine(); is reached. I am trying to send data with writeBytes(command); where command is a string. Any suggestions? thanks.

writebytes to readline
Stop right there. If you're using readLine() you're using BufferedReader, which is a Reader, which means you should be using a Writer to talk to it, which means you should be using a BufferedWriter, and as you're reading lines you must write lines, which means writing a line terminator (which you aren't presently doing), which means you should use BufferedWriter.newline().
Or PrintWriter.println(), but don't forget to check for errors, as it swallows exceptions.

Don't directly use readLine
Instead try this
If( inFromClient.ready()){
// read string here.
}
It might be possible that buffer is not ready and you are trying to read. So it can create problem.

Broken pipe using DataInputStream and DataOutputStream and sockets

I set up a client and server sockets. When I use classes ObjectOutputStream and ObjectInputStream and the method readObject/writeObject everything works fine.
It simulates communication with a robot that I know for sure interprets correctly only method
DataOutputStream.writeBytes.
So I set up the new architecture for simulation since the robot is not available for testing on a daily basis.
In the following code where ObjectOutputStream/ObjectInputStream readObject/writeObject were replaced with DataInputStream/DataOutputStream writeBytes and IOutils.toByteArray.
The server socket correctly receives the message but when it tries to write back a response I get a broken pipe as if the connection was closed somewhere.
Notice that I never close sockets or streams because the robot can answer even after 30 seconds.
Any help to make DataOutputStream.writeBytes work would be appreciated.
Here's the non-working code:
Client:
Socket serverSocket = new Socket("server", 9899);
DataOutputStream outputStream = new DataOutputStream(serverSocket.getOutputStream());
//ObjectOutputStream outputStream = new ObjectOutputStream(serverSocket.getOutputStream());
//outputStream.writeObject("\n" + "message" + "\r");
outputStream.writeBytes("\n" + "message" + "\r");
outputStream.flush();
DataInputStream inputStream = new DataInputStream(serverSocket.getInputStream());
//ObjectInputStream inputStream = new ObjectInputStream(serverSocket.getInputStream());
byte [] bytes = IOUtils.toByteArray(inputStream);
String serverResponse = new String(bytes,"UTF-8");
// String serverResponse = (String)inputStream.readObject();
Server:
ServerSocket serverSocket = new ServerSocket(9899);
while (true) {
Socket socket = serverSocket.accept();
//ObjectInputStream inputStream = new ObjectInputStream(socket.getInputStream());
DataInputStream inputStream = new DataInputStream(socket.getInputStream());
byte [] bytes = IOUtils.toByteArray(inputStream);
String message = new String(bytes,"UTF-8");
//String message = (String) inputStream.readObject();
Thread.sleep(15000);
//ObjectOutputStream outputStream = new ObjectOutputStream(socket.getOutputStream());
DataOutputStream outputStream = new DataOutputStream(socket.getOutputStream());
//outputStream.writeObject("server response");
outputStream.writeBytes("server response"); //EXCEPTION THROWN HERE FOR BROKEN PIPE
outputStream.flush();
}
Thanks for your time

IOUtils.toString(InputStream) must read the stream until its end, which would imply that the peer has disconnected. So you can't write to it.
If you're exchanging Strings with data streams you should use writeUTF() and readUTF().
Or read and write lines, with a BufferedReader/Writer.