Cosc 4755

1. Cosc 4755 Mobile networking Overview and Stream, Socket, and Datagram.

2. A Overview • Generic Connection Framework (GCF) • In Javax.microedition.io • Now includes files, more network protocols, smart cards, RFID cards, bluetooth, and bar codes. • And is being ported back to Java SE as JSR 197

3. Some Connection Schemes

4. Implemented under profiles Normally implemented, but carrier or handset may not.

5. Common Connections • Connector class is the abstracted view • Like when we used for file access. • Connection interface, generic connection • defines the close method • DatagramConnection interface, defines actions for a datagram connection, like UDP • Datagram interface, abstract interface for a datagram, which are bidirectional, extending the DataInput and DataOutput interfaces • StreamConnection, defines actions on a stream connection, such as TCP • bidirectional, uses the InputConnection and OutputConnection • ContentConnection interface, supports passes content encoded through a well-known codec • Video, audio, images.

6. Permission for Network Connection • Network applications require privilege, which is imposed by the MIDLet. • This ensures that unauthorized network connection do not result in data use charges. • On a phone, may require sign app • At min, requires the JAD to specify the privileges they require, set in the JAD attributes MIDlet-Permissions • See Pg 327 in the book for more info. • In the emulators, you app's runs as untrusted and connections are available if the user grants permission

7. URL syntax • scheme://user:password@host:port/path;parameters • Where • scheme is the protocol (ie http, file, etc) • user is the username, which is optional • password is the password for the username, also optional • host is the fully qualified domain name or address • port is the optional port number, scheme provides the default • path is the path on the remote end • the format varies by scheme. • Parameters are optional parameters, depends on scheme.

8. typical network code. String url = "socket://www.nowhere.com:3012"; … StreamConnection c = null; InputStream s = null; try { c = (StreamConnection)Connector.open(url); s = c.openInputStream(); intch; while ((ch = s.read()) != -1) { //read every character until end of file (-1). } } catch (ConnectionNotFoundException e) { …} catch (IllegalArgumentException e) { …} catch (IOException e) { …} finally { if (s != null) s.close(); if (c != null) c.close(); }

9. StreamConnection • Is the general method to open a network connection. • only provides openDataInputStream, openInputStream, openDataOutputStream, openOutputStream, and close methods. • The following inherit StreamConnection • CommConnection, ContentConnection, HttpConnection, HttpsConnection, SecureConnection, SocketConnection

10. SocketConnection • SocketConnection, provides us with the TCP connection (as does StreamConnection) • Provides methods some methods like we use in java SE and general UNIX socket programming. • String getAddress() • Gets the remote address to which the socket is bound.   • String getLocalAddress() • Gets the local address to which the socket is bound.   • intgetLocalPort() • Returns the local port to which this socket is bound.   • intgetPort() • Returns the remote port to which this socket is bound.   • intgetSocketOption(byte option) • Get a socket option for the connection.   • void setSocketOption(byte option, int value) • Set a socket option for the connection.

11. SocketConnection (2) • Byte Option • DELAY: Socket option for the small buffer writing delay. • KEEPALIVE: Socket option for the keep alive feature. • LINGER: Socket option for the linger time to wait in seconds before closing a connection with pending data output. • RCVBUF: Socket option for the size of the receiving buffer. • SNDBUF: Socket option for the size of the sending buffer. • Example • s.setSocketOption(SocketConnection.DELAY,0); • basically like flush(), send small packets. • int x = s.getSocketOption(SocketConnection.RCVBUF); • how big is the receive buffer?

12. Socket Example import javax.microedition.io.*; import java.io.*; String url = "socket://Somewhere.com:3012"; try { //connection should be it own method too. sock = (SocketConnection)Connector.open(url); in = new InputStreamReader(sock.openInputStream()); out = new OutputStreamWriter(sock.openOutputStream()); writeLine("Hi from a phone."); System.out.println("Wrote to System"); System.out.println("Now Waiting on input"); String from = getLine(); System.out.println("Server said:"+from); } catch (ConnectionNotFoundException e) { System.out.println("Something happened, ConnectionNotFoundException"); } catch (IllegalArgumentException e) { System.out.println("Something happened, IllegalArgumentException"); } catch (IOException e) { System.out.println("Something happened, IOExecption"); } finally { try { //close should be it's own method too. if (sock != null) sock.close(); if (in != null) in.close(); if (out != null) out.close(); } catch (IOException ex) { sock=null; in =null; out=null; } } • And getLine and writeLine methods: public void writeLine(String to) { to +="\n"; if (out!= null) { try { out.write(to.toCharArray(), 0, to.length()); } catch (IOException e) { label.setText("Failed to write"); } } } public String getLine() { // read from network port and have default value String from = ""; char ch; inti; if (in != null) { try { i = in.read(); while (i != -1 && (char) i != '\n') { from += (char) i; i = in.read(); } } catch (IOException e) { from = "AWGH!!!"; } } return (from); }

13. Datagram and DatagramConnection • Datagram and DatagramConnection are for UDP networking. • These work differently then Stream and Socket connection. • A datagramConnection, sends/receives a datagram. • There is no methods for OpenInputData and openOutputData streams. • A datagramConnection can be a client or server

14. DatagramConnection • like everything else, uses connector. • DatagramConnectiondgc = null; • Client • url = "data://somwhere.com:3012"; • dgc = (DatagramConnection)Connector.open(url); • Server • url = "data://:3012"; //note no hostname! • dgc = (DatagramConnection)Connector.open(url);

15. datagram • UDP is a connectionless protocol • A datagram is the packet, which is sent or received. • Datagram has • buffer, which is the data • offset, which is the pointer to current read or write • length, which is the size of the buffer. • header information is also available • There is also a reset method, to reuse the datagram.

16. datagram (2) • The datagram uses the DataInput/Output methods • readBoolean, writeBoolean • readByte, WriteByte • readChar, writeChar • readFloat, writeFloat • readShort, writeShore • readInt, writeInt • readLong, writeLong • readUTF, writeUTF • readFully, write • read/write an array of bytes.

17. datagram (3) • Again, we can work with Strings instead. • Using the String functions to read/write bytes. • datagram has the two following methods (and the constructor) • byte[] = getData() //return the data buffer • setData(byte[] b, int offset, int length) //set buffer

18. UDP example import javax.microedition.io.*; import java.io.*; String url = "datagrame://somewhere.com:3012"; DatagramConnectiondgc = null; Datagram d; String s = "Hello World"; byte m[] = s.getBytes(); String t; try { dgc = (DatagramConnection) Connector.open(url); //create the datagram with the data d = dgc.newDatagram(m,m.length); //send the datagram dgc.send(d); //now receive a datagram d.reset(); //reset for reuse dgc.receive(d); t = new String(d.getData()); System.out.println("Recieved: "+t); } catch (IOException ex) { …}

19. Server side. • Sounds like an odd idea for a phone, but there are a number of reason • Mainly, what is called, "push" data sent to the phone. email and other information • UDP uses the same as before, no host name and use receive method. • TCP, uses ServerSocketConnection method.

20. ServerSocketConnection • Similar to a UNIX methods (java's too) • Like UDP, no host is url line. url = "socket://:3012"; • There is an acceptAndOpen() method • returns a SocketConnection • useful methods • String getLocalAddress() • intgetLocalPort()

21. ServerSocketConnection Example import javax.microedition.io.*; import java.io.*; private InputStreamReader in = null; private OutputStreamWriter out = null; private SocketConnection sock = null; private ServerSocketConnectionssc = null; String url="socket://:3012"; try { ssc = (ServerSocketConnection) Connector.open(url); System.out.println("localaddress is "+ssc.getLocalAddress()); sock = (SocketConnection)ssc.acceptAndOpen(); in = new InputStreamReader(sock.openInputStream()); out = new OutputStreamWriter(sock.openOutputStream()); //just like SocketConnection now //and close the sock, in, and out ssc.close(); } catch (IOException ex) { }

22. Server connections. • This work until you close the application. • To have data pushed, use the MIDlet-push field in application descriptor. • MIDlet-Push-1: socket://:3012, NameMIDlet,* • Now when data is received on port 3012, the server will be started up to respond to it. • Also can use the PushRegistery, part of the Wireless message API (WMA 1.1)

23. Q A &