How to get String from DataInputStream in Java?

Question

I am working on an application consisting of sockets. It needs to transfer a String value from the client(android device) to the server(my PC running Ubuntu). On the server side code, I need to store the value being transferred via socket in a String variable.

Here is the code I am using to send the String value to the server.

//instantiating the socket object for the client
Socket client = new Socket("192.168.0.103", port);

OutputStream outToServer = client.getOutputStream();

DataOutputStream out = new DataOutputStream(outToServer);

String msg = "My String Value";

//Message to be send to server
out.writeUTF(msg);

//Closing the client's socket. No connections after this.
client.close();

And here is the code I am using to get the String value at the server.

//Server object. Stores the reference to the socket object returned by the accept()
//The returned socket object contains established connection to the client.
Socket server = serverSocket.accept();

DataInputStream in = new DataInputStream(server.getInputStream());
System.out.println(in.readUTF());
//This prints "My String Message"

//Something like this i want to do.
String msg = in.readUTF();

//closing the server socket. No connection now.
server.close();

Right now what is happening is the program at server side is getting stuck at line :

String msg = in.readUTF();

What is the correct way of storing the String value from DataInputStream into a String variable?

You're reading it twice, but only writing it once. You can't read it twice if you only write it once. — David Conrad, Jan 07 '15 at 20:14
Good catch!. But still I am looking for the best way to do so. — priyankvex, Jan 07 '15 at 20:19
You already have the best way to do so, subject only to the 16-bit limitation. — user207421, Jan 07 '15 at 20:20
so... `String msg = in.readUTF(); System.out.println(msg);` ? — njzk2, Jan 07 '15 at 20:23

score 1 · Accepted Answer · answered Jan 07 '15 at 20:17

You write the data once, and on the other side you try to read it twice, but there is only one copy of the data there to be read.

DataInputStream in = new DataInputStream(server.getInputStream());
System.out.println(in.readUTF());
//This prints "My String Message"

This also consumes the only copy of the string that was present on the stream.

Right now what is happening is the program at server side is getting stuck at line:

String msg = in.readUTF();

When you call in.readUTF() a second time, it waits for the client to send more data (another string), but since the client never sends any more data, it will wait forever (or until you kill it, or the connection times out).

Dani Torres · Answer 2 · 2018-02-21T19:42:01.140

0

As @david-conrad explained, when you first read, the input buffer becomes empty for next reads, so the solution remains in buffering first the content into a string, and then you can use that string for anything, (println, for example).

DataInputStream in = new DataInputStream(server.getInputStream());
String msg = in.readUTF();
System.out.println(msg);

edited Feb 21 '18 at 19:42

answered Feb 21 '18 at 19:26

Dani Torres

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How to get String from DataInputStream in Java?

2 Answers2