Network Clients - Java - page 517

Solution

Construct an ObjectInputStream or ObjectOutputStream from the socket's getIn-
putStream() or getOutputStream() .

Discussion

Object serialization is the ability to convert in-memory objects to an external form that can
be sent serially (a byte at a time). This is discussed in Saving and Restoring Java Objects .

This program (and its server) operate one service that isn't normally provided by TCP/IP, be-
cause it is Java-specific. It looks rather like the DaytimeBinary program in the previous re-
cipe, but the server sends us a Date object already constructed. You can find the server for
this program in Returning a Response (String or Binary) ; Example 13-7 shows the client
code.

Example 13-7. DaytimeObject.java
public public class DaytimeObject {

/** The TCP port for the object time service. */
public

class DaytimeObject

public static static final final short short TIME_PORT = 1951 ;

public public static void main ( String [] argv ) {

String hostName ;
iif ( argv . length == 0 )
hostName = "localhost" ;

static void

else else

hostName = argv [ 0 ];

try try {

Socket sock = new

new Socket ( hostName , TIME_PORT );
ObjectInputStream is = new new

BufferedInputStream ( sock . getInputStream ()));

new ObjectInputStream ( new

// Read and validate the Object
Object o = is . readObject ();
iif ( o == null null ) {

System . err . println ( "Read null from server!" );
} else else iif (( o instanceof instanceof Date )) {

// Valid, so cast to Date, and print
Date d = ( Date ) o ;
System . out . println ( "Server host is " + hostName );
System . out . println ( "Time there is " + d . toString ());