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Java Cookbook
book

Java Cookbook

by Ian F. Darwin
June 2001
Intermediate to advanced content levelIntermediate to advanced
888 pages
21h 1m
English
O'Reilly Media, Inc.
Content preview from Java Cookbook

Handling Network Errors

Problem

You want more detailed reporting than just IOException if something goes wrong.

Solution

Catch a greater variety of exception classes. There are several subclasses of SocketException; the most notable of these are ConnectException and NoRouteToHostException. The names are self-explanatory: the first means that the connection was refused by the machine at the other end (the server machine), and the second completely explains the failure. Example 15-3 is an excerpt from the Connect program, enhanced to handle these conditions.

Example 15-3. ConnectFriendly.java

/* Client with error handling */
public class ConnectFriendly {
    public static void main(String[] argv) {
        String server_name = argv.length == 1 ? argv[0] : "localhost";
        int tcp_port = 80;
        try {
            Socket sock = new Socket(server_name, tcp_port);

            /* Finally, we can read and write on the socket. */
            System.out.println(" *** Connected to " + server_name  + " ***");
            /* ... */

            sock.close(  );

        } catch (UnknownHostException e) {
            System.err.println(server_name + " Unknown host");
            return;
        } catch (NoRouteToHostException e) {
            System.err.println(server_name + " Unreachable" );
            return;
        } catch (ConnectException e) {
            System.err.println(server_name + " connect refused");
            return;
        } catch (java.io.IOException e) {
            System.err.println(server_name + ' ' + e.getMessage(  ));
            return;
        }
    }
}
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Publisher Resources

ISBN: 0596001703Supplemental ContentCatalog PageErrata