Here is a simple server for those who are starting studying sockets or just needs a simple socket server example for reuse while writing your own behavior.
Features:
- A client should enter a string and the server would answer the same string, with each symbol in up case, when possible.
- Default port at 8080.
- One client at time.
- No multi threading. I said its a simple server.
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.ServerSocket;
import java.net.Socket;
public class Server {
private static final int DEFAULT = 8080;
public Server() {
this(DEFAULT);
}
public Server(int port) {
ServerSocket sock;
try {
sock = new ServerSocket(port);
System.out.println(String.format("Listening on port %d.", port));
while (true) {
try {
Socket client = sock.accept();
System.out.println("A new connection was accepted.");
BufferedReader in = new BufferedReader(
new InputStreamReader(client.getInputStream()));
OutputStreamWriter out = new OutputStreamWriter(client
.getOutputStream());
String input = "";
while (!input.equals("exit")) {
input = in.readLine();
if (input.equals("shutdown")) {
System.exit(0);
}
out.write(input.toUpperCase() + "\r\n");
out.flush();
}
in.close();
out.close();
client.close();
System.out.println("Connection closed.");
} catch (NullPointerException npe) {
System.out.println("Connection closed by client.");
}
}
} catch (IOException ioe) {
System.err.println(ioe);
System.exit(-1);
}
}
public static void main(String[] args) throws IOException {
new Server();
}
}
Usage:
$ javac Server.java
$ java Server
Listening on port 8080.
In another terminal:
$ telnet localhost 8080
Trying ::1…
Connected to localhost.
Escape character is ‘^]’.
hi
HI
The quick brown fox jumps over the lazy dog.
THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG.
exi
EXI
exit
EXIT
Connection closed by foreign host.
