I have this TCP server running Because UDP server was able to accept large packets but ISP blocks my UDP packets even i have Public IP and Static services. But now decided to change it to TCP but i have a large stack now to replace with UDP to TCP.
Here is the server which is running but it does not at once receive a large packet, how can i increase it to unlimited or maximum size or etc?
1) Is there any way with this?
public void run()
{
while(true)
{
byte[] buf=new byte[5024]; <<< not helping!!
int bytes_read = 0;
try {
bytes_read = sockInput.read(buf, 0, buf.length);
String data = null;
data = new String(buf, 0, bytes_read);
System.out.println("[TCP]: incomeing data: " + bytes_read + " bytes, data=" +data);
}
}
2) Is there any way with this?
public TCPHandler(Socket sock) throws IOException
{
sock.setReceiveBufferSize(10*1024 +1024); //<<<<< not helping !!!
sock.setSendBufferSize(10*1024+1024);
this.sock = sock;
sockInput = sock.getInputStream();
sockOutput = sock.getOutputStream();
this.myThread = new Thread(this);
}
None is allowing me to handle large so that i can switch from UDP to TCP. Any ideas!!
TCP and UDP are different. TCP is not a packet-based protocol, it is a stream based protocol. Your data will arrive in order, and un-corrupted, but it will not necessarily all arrive at once.
What you should do is prefix each set 'packet' with a length. When you receive data, first read the length value, and then continue reading chunks from the socket until you have the amount of data required.
You shouldn't care how TCP splits your messages into packets and how many times you must read to get a full message. Just read until the end of the message has been reached, and then return all the bytes of the message.
Knowing when the message has been read completely depends on your protocol. You could choose to send only one message per connection, or you could send the length of the message before the message, or use some marker byte.
Note that you shouldn't use new String(byte[]) without specifying an encoding (and use the same when calling String.getBytes()), especially if you transfer from one machine to another, since both machines could have a different default encoding.
The trouble you're having is how InputStreams work. When you call read(buf,offset,length) it doesn't always read length bytes everytime. It simply reads what is available() on the InputStream, and returns the number of bytes it read. So you need to continue to call read until you've actually read length bytes.
int len = 0;
int expectedLength = sockInput.readInt();
byte[] buf = new byte[ expectedLength ];
while( len != buf.length ) {
len += sockInput.read( buf, len, buf.length );
}
// now you have a buffer with expectedLength data in it.
You can also look at using DataInputStream.readFully() by wrapping your
DataInputStream ds = new DataInputStream( sock.getInputStream() );
ds.readFully( buf, 0, buf.length );
http://docs.oracle.com/javase/6/docs/api/java/io/DataInputStream.html
But if you're really just after a String you should do this:
Reader reader = new InputStreamReader( sockInput.getInputStream(), "UTF-8" );
Same rules for read( char[], offset, length ) as read( byte[], offset, length )
A TCP is a stream of bytes you can get a portion of, one or more messages is a single read.
With UDP packets of more than 532 bytes, the packet can be broken up, so you have the same potential problem.
A simple way to encode message is to send the length first.
final DataOutputStream out = new DataOutputStream(new BufferedOutputStream(socket.getOutputStream()));
final DataInputStream in = new DataInputStream(new BufferedInputStream(socket.getInputStream()));
public void writeMessage(String text) {
out.writeUTF(text);
}
public String readMessage() {
return in.readUTF();
}
read/write UTF sends the length first and followed by the content
Related
In my application I'm create a socket to do communication between a client and a server. There are two types of messages are passing which they differ in-terms of the length of the data. One message type has only one byte, while the other one is of variable length. I was trying to use a single TCP connection to handle both situations, but so far failed. Could someone please tell me what would be the ideal approach for this. Is using two connections with different port numbers would be the best approach?
Note that It is impossible to use socket.io in my project due to external constraints.
here's the reading code i'm using:
Socket socket = new Socket( dstAddress, dstPort );
InputStream inputStream = socket.getInputStream();
try( ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream( 1024 ) )
{
byte[] buffer = new byte[1024];
int bytesRead;
while( ( bytesRead = inputStream.read( buffer ) ) != -1 )
{
byteArrayOutputStream.write( buffer, 0, bytesRead );
}
}
catch( Exception e )
{
e.printStackTrace();
}
Thanks
you need to design your own communication protocol, like http for example, but of course much simpler. and implement decoder/encoder on both sides
I am reading TCP packets that I use to display an image. Each packet is supposed to have a 1025 length. And each time, I get 128 lines, I draw an image.
SO I begin by initializing
s = new Socket(ip, port);
stream = s.getInputStream();
byte[] tmpBuffer = new byte[1025];
byte[] finalBuffer = new byte[128 * 1025];
int count_lines =0
and then I read stream by stream of length 1025,
while((read = stream.read(tmpBuffer, 0, tmpBuffer.length)) != -1){
System.arraycopy(tmpBuffer, 1, finalBuffer, count_lines * 1025, 1025);
count_lines++;
if(count_lines == 128) break;
}
The problem is when I log the read integer, I get a bunch of 1025 but sometimes (apparently randomly) 423 or 602 (noticing that 423+602=1025)
Am I going wrong with the TCP reading or is there a problem on the server side ?
Am I going wrong with the TCP reading or is there a problem on the server side ?
In TCP you have only a stream of bytes. You have messages nor control over packets which are typically no more than 1532 bytes long.
You have to have your own protocol to handle sending of messages.
inputStream.read(buffer) will read between 1 byte and buffer.length and you can't ignore the actual length read as you are doing.
If you want to read into a buffer of a known length, you can use
DataInputStream dis = new DataInputStream(socket.getInputStream());
byte[] finalBuffer = new byte[128 * 1025];
dis.readFully(finalBuffer);
The readFully reads as much as it can at a time until the byte[] has been fully read.
A more flexible protocol is to send the length first.
public static void write(DataOutputStream out, byte[] bytes) {
out.writeInt(bytes.length());
out.write(bytes);
}
public static byte[] read(DataInputStream in) {
int length = in.readInt();
byte[] bytes = new byte[length];
in.readFully(bytes);
return bytes;
}
This way, whatever length of data you send, you will recieve in the same manner.
I've been playing around with transferring data between a test client (written in Java) and a server (written in C#/.NET).
I tried TCP clients and servers, but there has been and current is a problem flushing the stream. I realize flush doesn't always flush the stream, so I'm wondering if there is any way to flush/send a stream without .flush() or in a more reliable way?
Currently, the important part of the client looks like this (message is a string, serverSocket is a Socket object):
OutputStream output = serverSocket.getOutputStream();
byte[] buffer = message.getBytes();
int length = buffer.length;
output.write(ByteBuffer.allocate(4).putInt(length).array());
output.write(buffer);
output.flush();
and the server looks like this:
NetworkStream stream = client.GetStream ();
byte[] sizeBuffer = new byte[4];
int read = stream.Read (sizeBuffer, 0, 4);
int size = BitConverter.ToInt32 (sizeBuffer, 0);
Databaser.log ("recieved byte message denoting size: " + size);
byte[] messageBuffer = new byte[size];
read = stream.Read (messageBuffer, 0, size);
string result = BitConverter.ToString (messageBuffer);
Databaser.log ("\tmessage is as follows: '" + result + "'");
Where, if it's not evident from the code, the client sends 4 bytes, which are combined into a 32 bit integer which is the length of the message. Then I read in the message based on that length and have build in converters translate it into a string.
As I said, I'm wondering how to flush the connection? I know this code isn't perfect, but I can change it back to when I used TCP and UTF exclusive string messaging over the network, but either way, the connection doesn't send anything from the client until the client shuts down or closes the connection.
Maybe the problem is in the byte order. I have an application which send from a tablet (java) to a C# application (Windows Intel), I used similar to what you've done, except in the following
ByteBuffer iLength = ByteBuffer.allocate(4);
iLength.order(ByteOrder.LITTLE_ENDIAN);
iLength.putInt(length);
output.write(iLength.array(), 0, 4);
output.write(buffer);
output.flush();
Java uses BIG-ENDIAN and Intel uses LITTLE-ENDIAN bytes order.
Hi I have created a server socket for reading byte array from socket using getInputStream, But getInputStream.read is not exiting after endof data reaches. Below is my code.
class imageReciver extends Thread {
private ServerSocket serverSocket;
InputStream in;
public imageReciver(int port) throws IOException
{
serverSocket = new ServerSocket(port);
}
public void run()
{
Socket server = null;
server = serverSocket.accept();
in = server.getInputStream();
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte buffer[] = new byte[1024];
while(true){
int s = 0;
s = in.read(buffer); //Not exiting from here
if(s<0) break;
baos.write(buffer, 0, s);
}
server.close();
return;
}
}
From the client if I sent 2048 bytes, the line in.read(buffer) should return -1 after reading two times, but it waiting there to read for the third time. How can I solve this ?
Thanks in advance....
Your server will need to close the connection, basically. If you're trying to send multiple "messages" over the same connection, you'll need some way to indicate the size/end of a message - e.g. length-prefixing or using a message delimiter. Remember that you're using a stream protocol - the abstraction is just that this is a stream of data; it's up to you to break it up as you see fit.
See the "network packets" in Marc Gravell's IO blog post for more information.
EDIT: Now that we know that you have an expected length, you probably want something like this:
int remainingBytes = expectedBytes;
while (remainingBytes > 0) {
int bytesRead = in.read(buffer, 0, Math.min(buffer.length, remainingBytes));
if (bytesRead < 0) {
throw new IOException("Unexpected end of data");
}
baos.write(buffer, 0, bytesRead);
remainingBytes -= bytesRead;
}
Note that this will also avoid overreading, i.e. if the server starts sending the next bit of data, we won't read into that.
If I send 2048 bytes, the line 'in.read(buffer)' should return -1 after reading two times.
You are mistaken on at least two counts here. If you send 2048 bytes, the line 'in.read(buffer)' should execute an indeterminate number of times, to read a total of 2048 bytes, and then block. It should only return -1 when the peer has closed the connection.
I am writing a java TCP client that talks to a C server.
I have to alternate sends and receives between the two.
Here is my code.
The server sends the length of the binary msg(len) to client(java)
Client sends an "ok" string
Server sends the binary and client allocates a byte array of 'len' bytes to recieve it.
It again sends back an "ok".
step 1. works. I get "len" value. However the Client gets "send blocked" and the server waits to receive data.
Can anybody take a look.
In the try block I have defined:
Socket echoSocket = new Socket("192.168.178.20",2400);
OutputStream os = echoSocket.getOutputStream();
InputStream ins = echoSocket.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(ins));
String fromPU = null;
if( (fromPU = br.readLine()) != null){
System.out.println("Pu returns as="+fromPU);
len = Integer.parseInt(fromPU.trim());
System.out.println("value of len from PU="+len);
byte[] str = "Ok\n".getBytes();
os.write(str, 0, str.length);
os.flush();
byte[] buffer = new byte[len];
int bytes;
StringBuilder curMsg = new StringBuilder();
bytes =ins.read(buffer);
System.out.println("bytes="+bytes);
curMsg.append(new String(buffer, 0, bytes));
System.out.println("ciphertext="+curMsg);
os.write(str, 0, str.length);
os.flush();
}
UPDATED:
Here is my code. At the moment, there is no recv or send blocking on either sides. However, both with Buffered Reader and DataInput Stream reader, I am unable to send the ok msg. At the server end, I get a large number of bytes instead of the 2 bytes for ok.
Socket echoSocket = new Socket("192.168.178.20",2400);
OutputStream os = echoSocket.getOutputStream();
InputStream ins = echoSocket.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(ins));
DataInputStream dis = new DataInputStream(ins);
DataOutputStream dos = new DataOutputStream(os);
if( (fromPU = dis.readLine()) != null){
//if( (fromPU = br.readLine()) != null){
System.out.println("PU Server returns length as="+fromPU);
len = Integer.parseInt(fromPU.trim());
byte[] str = "Ok".getBytes();
System.out.println("str.length="+str.length);
dos.writeInt(str.length);
if (str.length > 0) {
dos.write(str, 0, str.length);
System.out.println("sent ok");
}
byte[] buffer = new byte[len];
int bytes;
StringBuilder curMsg = new StringBuilder();
bytes =ins.read(buffer);
System.out.println("bytes="+bytes);
curMsg.append(new String(buffer, 0, bytes));
System.out.println("binarytext="+curMsg);
dos.writeInt(str.length);
if (str.length > 0) {
dos.write(str, 0, str.length);
System.out.println("sent ok");
}
Using a BufferedReader around a stream and then trying to read binary data from the stream is a bad idea. I wouldn't be surprised if the server has actually sent all the data in one go, and the BufferedReader has read the binary data as well as the line that it's returned.
Are you in control of the protocol? If so, I suggest you change it to send the length of data as binary (e.g. a fixed 4 bytes) so that you don't need to work out how to switch between text and binary (which is basically a pain).
If you can't do that, you'll probably need to just read a byte at a time to start with until you see the byte representing \n, then convert what you've read into text, parse it, and then read the rest as a chunk. That's slightly inefficient (reading a byte at a time instead of reading a buffer at a time) but I'd imagine the amount of data being read at that point is pretty small.
Several thoughts:
len = Integer.parseInt(fromPU.trim());
You should check the given size against a maximum that makes some sense. Your server is unlikely to send a two gigabyte message to the client. (Maybe it will, but there might be a better design. :) You don't typically want to allocate however much memory a remote client asks you to allocate. That's a recipe for easy remote denial of service attacks.
BufferedReader br = new BufferedReader(new InputStreamReader(ins));
/* ... */
bytes =ins.read(buffer);
Maybe your BufferedReader has sucked in too much data? (Does the server wait for the Ok before continuing?) Are you sure that you're allowed to read from the underlying InputStreamReader object after attaching a BufferedReader object?
Note that TCP is free to deliver your data in ten byte chunks over the next two weeks :) -- because encapsulation, differing hardware, and so forth makes it very difficult to tell the size of packets that will eventually be used between two peers, most applications that are looking for a specific amount of data will instead populate their buffers using code somewhat like this (stolen from Advanced Programming in the Unix Environment, an excellent book; pity the code is in C and your code is in Java, but the principle is the same):
ssize_t /* Read "n" bytes from a descriptor */
readn(int fd, void *ptr, size_t n)
{
size_t nleft;
ssize_t nread;
nleft = n;
while (nleft > 0) {
if ((nread = read(fd, ptr, nleft)) < 0) {
if (nleft == n)
return(-1); /* error, return -1 */
else
break; /* error, return amount read so far */
} else if (nread == 0) {
break; /* EOF */
}
nleft -= nread;
ptr += nread;
}
return(n - nleft); /* return >= 0 */
}
The point to take away is that filling your buffer might take one, ten, or one hundred calls to read(), and your code must be resilient against slight changes in network capabilities.