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.
Related
I'm developing an Android client app which talks to server via a plain TCP Socket, let's assume that the server ip 192.168.1.2 and the androdi device ip is 192.168.1.3.
I open the socket, i check if socket is connected (i get true as result) and after that i write a presentation message.
Here is my code
// scoket setup
Sockets = new Socket(addressToConnect, 2015);
s.setSoTimeout(2500);
setTcpNoDelay(true);
// if i'm connected
if (s.isConnected()) {
// wrapping streams
DataInputStream dis = new DataInputStream(s.getInputStream());
DataOutputStream dos = new DataOutputStream(s.getOutputStream());
// sending data
String presentationMessage = "Presentation message content--- TERM";
dos.write(presentationMessage.getBytes("UTF-8");
dos.flush();
// buffers
byte[] readBuffer = new byte[4096];
StringBuffer responseBuffer = new StringBuffer();
// read data until command terminator string is found
boolean readResponse = true;
while (readResponse) {
int dataBufferLength = dis.read(readBuffer);
String chunk = new String(readBuffer, 0, dataBufferLength, "UTF-8"));
responseBuffer.append(chunk);
readResponse = ! chunk.endWith("--- TERM");
}
// Process data here
} else {
// Notify missing connection here
}
// here i close the socket
When i execute this code the execution seems working like a charme until the first read which timesout.
Sniffing the used WIFI network with a third machine i can't see the connection establishment and the written stream even if the code doesn't throw any exception before the read timeout.
I granted the android.permission.INTERNET in manifest.
Are there some other permissions to grant? or what i'm doing wrong?
Executing the same code in a standard Java SE environment everything goes fine.
I'm testing the code on a Nexus 5, Nexus 9 and Samsung S3 and S4 and the project is compatible with API 14+
Edit: Fixed typo in code example
You are reading from dos and writing to dis. You should reverse that.
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.
I am having a real problem trying to find a solution to my problem and hope you guys could help. I have seen many socket examples online but have been unable to modify them for my use. Tbh, im struggling to even get an understanding of sockets. What I have been able to modify so far is below.
My problem, I believe is that my client program is not reading the incoming message from the server, could someone use my example to demonstrate where I am going wrong. Something in my mind tells me that my client socket closes before having a chance to read any incoming message. perhaps getting the client to wait until a message is recieved? If waiting is what is needed, how is this achieved? Thanks in advance.
CLIENT:
try {
Socket socket = new Socket("localhost", 55555);
PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
out.write(score);
BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
String rank = in.readLine();
System.out.println(rank);
in.close();
out.close();
socket.close();
}
catch(Exception e) {
System.out.print("Whoops! It didn't work!\n");
}
SERVER:
try {
System.out.println("Waitng for client to connect.....");
ServerSocket server = new ServerSocket(55555);
Socket socket = server.accept();
System.out.print("Client has connected!\n");
BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
String score = (in.readLine());
scor = Long.parseLong(score);
leaderboard(); ///// A METHOD THAT USES LONG SCORE TO CALCULATE RANKING- RETURNS A STRING VALUE CALLED RANK
PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
System.out.print("Sending rank: " + rank);
out.write(rank);
out.close();
socket.close();
server.close();
}
catch(Exception e) {
System.out.print("Whoops! It didn't work!\n")`enter code here`;
}
Your code looks fine...
On your client program you're writing a line using:
out.write(score);
could you change this to:
out.println(score);
Also do the same on your server's program to take care of the reply:
out.println(rank);
Let me know how you go..
also if this helped, don't forget to upvote/mark this as a solution ;)
cheers
(Btw,as to what caused the problem:: in.read'LINE'() waits for the end of a line or newline(\n) for the string value to be saved. if you use out.write() then you have to and a newline character(\n) manually for the string to be read completely. if you use out.printline, then \n is added automatically to every string sent.
The readline method in your program was waiting for a newline character, which is why your program was stuck in that spot)
I have a Socket listening on some x port.
I can send the data to the socket from my client app but unable to get any response from the server socket.
BufferedReader bis = new BufferedReader(new
InputStreamReader(clientSocket.getInputStream()));
String inputLine;
while ((inputLine = bis.readLine()) != null)
{
instr.append(inputLine);
}
This code part reads data from server.
But I can't read anything from server until unless the Socket on the server is closed.
Server code is not under my control to edit something on it.
How can I overcome this from client code.
Thanks
Looks like the server may not be sending newline characters (which is what the readLine() is looking for). Try something that does not rely on that. Here's an example that uses the buffer approach:
Socket clientSocket = new Socket("www.google.com", 80);
InputStream is = clientSocket.getInputStream();
PrintWriter pw = new PrintWriter(clientSocket.getOutputStream());
pw.println("GET / HTTP/1.0");
pw.println();
pw.flush();
byte[] buffer = new byte[1024];
int read;
while((read = is.read(buffer)) != -1) {
String output = new String(buffer, 0, read);
System.out.print(output);
System.out.flush();
};
clientSocket.close();
To communicate between a client and a server, a protocol needs to be well defined.
The client code blocks until a line is received from the server, or the socket is closed. You said that you only receive something once the socket is closed. So it probably means that the server doesn't send lines of text ended by an EOL character. The readLine() method thus blocks until such a character is found in the stream, or the socket is closed. Don't use readLine() if the server doesn't send lines. Use the method appropriate for the defined protocol (which we don't know).
For me this code is strange:
bis.readLine()
As I remember, this will try to read into a buffer until he founds a '\n'. But what if is never sent?
My ugly version breaks any design pattern and other recommendations, but always works:
int bytesExpected = clientSocket.available(); //it is waiting here
int[] buffer = new int[bytesExpected];
int readCount = clientSocket.read(buffer);
You should add the verifications for error and interruptions handling too.
With webservices results this is what worked for me ( 2-10MB was the max result, what I have sent)
Here is my implementation
clientSocket = new Socket(config.serverAddress, config.portNumber);
BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
while (clientSocket.isConnected()) {
data = in.readLine();
if (data != null) {
logger.debug("data: {}", data);
}
}
inFromClientR.readLine() never stops. any ideas? Am I forgetting something?
Server:
/*{ some code:
send a file with a dataoutputstream to client using a new port(4000) and when transfer is done i want a responce message (e.g. OK) send back to server in the old port(6000)
}*/
ServerSocket listenTransferSocket = new ServerSocket(6000);
Socket connectionTransferSocket = listenTransferSocket.accept();
BufferedReader inFromClientR =
new BufferedReader(new InputStreamReader(connectionTransferSocket.getInputStream()));
System.out.println("Client's response to Transfer: " +inFromClientR.readLine());
Client:
/*{ some code:
receive the file on port (4000) and then the responce is sent to server using the following commands
}*/
Socket fileTransferSocket = new Socket("localhost", 6000);
DataOutputStream outToServerR =
new DataOutputStream(fileTransferSocket.getOutputStream());
outToServerR.writeBytes("Transfer completed " +'\n');
BufferedReader#readLine() tries to fill its buffer with 8192 bytes, regradless of any linefeeds it find meanwhile. Since you have the connection open, the receiving side will wait until 1) you have sent 8192 bytes, or 2) closes the connection.
You would be better off using some other framing mechanism, maybe an ObjectOutputStream/ObjectInputStream.
String line = null;
while ((line = inFromClientR.readLine()) != null) {
// do sth
}