various refinements to network implementation

The main idea is to make DatagramChannel and *SocketChannel behave in
a way that more closely matches the standard, e.g. allow binding
sockets to addresses without necessarily listening on those addresses
and accept null addresses where appropriate.  It also avoids multiple
redundant DNS lookups.

This commit also implements CharBuffer and BindException, and adds the
Readable interface.

classpath/java/net/InetSocketAddress.java

@@ -11,15 +11,25 @@
 package java.net;
 
 public class InetSocketAddress extends SocketAddress {
+  private final String host;
   private final InetAddress address;
   private final int port;
 
-  public InetSocketAddress(String host, int port) throws UnknownHostException {
-	  this.address = InetAddress.getByName(host);
-	  this.port = port;
+  public InetSocketAddress(String host, int port) {
+    InetAddress address;
+    try {
+      address = InetAddress.getByName(host);
+      host = address.getHostName();
+    } catch (UnknownHostException e) {
+      address = null;
+    }
+    this.host = host;
+    this.address = address;
+    this.port = port;
   }
   
   public InetSocketAddress(InetAddress address, int port) {
+    this.host = address.getHostName();
     this.address = address;
     this.port = port;
   }
@@ -29,10 +39,27 @@ public class InetSocketAddress extends SocketAddress {
   }
   
   public String getHostName() {
-	return address.getHostName();
+    return host;
   }
 
   public int getPort() {
     return port;
   }
+
+  public boolean equals(Object o) {
+    if (o instanceof InetSocketAddress) {
+      InetSocketAddress a = (InetSocketAddress) o;
+      return a.address.equals(address) && a.port == port;
+    } else {
+      return false;
+    }
+  }
+
+  public int hashCode() {
+    return port ^ address.hashCode();
+  }
+
+  public String toString() {
+    return getHostName() + ":" + port;
+  }
 }