Easy-to-understand multicast (textbook)

1. repeatedly broadcast a piece of news.

Code:

1. Package mulsocket. frombook;
3. Import java.net .*;
5. Public class broadcast extends thread {
6. String S = "today's weather is fine, good scenery everywhere! ";
7. Int Port = 5858; // The multicast port.
8. Inetaddress group = NULL; // multicast group
9. Multicastsocket socket = NULL; // multicast socket
11. Broadcast (){
12. Try {
13. Group = inetaddress. getbyname ("239.20.8.0"); // you can specify 239.20.8.0 as the multicast group.
14. Socket = new multicastsocket (port); // The multicast socket will be broadcast on the port.
15. Socket. settimetolive (0); // The data packet sent by the Multi-Point broadcast socket is in the local network.
16. Socket. joingroup (group );
17. // Join the multicast group. After joining the group, the datagram sent by the socket can be received by the member added to the group.
18. } Catch (exception e ){
19. }
20. }
22. Public void run (){
23. While (true ){
24. Try {
25. Datagrampacket packet = NULL; // The datagram to be broadcast
26. Byte data [] = S. getbytes ();
27. Packet = new datagrampacket (data, data. length, group, Port );
28. System. Out. println (new string (data ));
29. Socket. Send (packet); // broadcast Datagram
30. Sleep (2000 );
31. } Catch (exception e ){
32. System. Out. println (E. tostring ());
33. Break;
34. }
35. }
36. }
38. Public static void main (string ARGs []) {
39. New broadcast (). Start ();
40. }
41. }

2. Join the multicast group to receive Broadcast Data

Code:

1. Package mulsocket. frombook;
3. Import java.net .*;
4. Import java. AWT .*;
5. Import java. AWT. event .*;
6. Import javax. Swing .*;
8. Public class receive extends jframe implements runnable, actionlistener {
9. Private Static final long serialversionuid = 1l;
10. Int port; // multicast Port
11. Inetaddress group = NULL; // the address of the multicast group
12. Multicastsocket socket = NULL; // multicast socket
14. Jbutton startreceive, stopreceive;
15. Jtextarea showarea;
16. Thread thread; // The thread responsible for receiving information
17. Boolean stop = false;
19. Public receive (){
20. Super ("timed receiving information ");
21. Thread = new thread (this );
22. Startreceive = new jbutton ("start receiving ");
23. Stopreceive = new jbutton ("stop receiving ");
24. Startreceive. addactionlistener (this );
25. Stopreceive. addactionlistener (this );
26. Showarea = new jtextarea (10, 10 );
27. Jpanel North = new jpanel ();
28. North. Add (startreceive );
29. North. Add (stopreceive );
30. Container con = getcontentpane ();
31. Con. Add (North, borderlayout. North );
32. Con. Add (New jscrollpane (showarea), borderlayout. center );
33. Port = 5858;
34. Try {
35. // Initialize in one breath
36. Group = inetaddress. getbyname ("239.20.8.0 ");
37. Socket = new multicastsocket (port );
38. Socket. joingroup (group );
39. } Catch (exception e ){
40. }
41. Setdefaclocloseoperation (jframe. exit_on_close );
42. Setsize (320,300 );
43. Validate ();
44. Setvisible (true );
45. }
47. Public void actionreceivmed (actionevent e ){
48. If (E. getsource () = startreceive ){
49. If (! (Thread. isalive ())){
50. Thread = new thread (this );
51. Stop = false;
52. }
53. Try {
54. Thread. Start ();
55. } Catch (exception ee ){
56. }
57. }
58. If (E. getsource () = stopreceive ){
59. Stop = true;
60. }
61. }
63. Public void run (){
64. While (true ){
65. Byte data [] = new byte [8192];
66. Required rampacket packet = NULL;
67. Packet = new datagrampacket (data, data. length, group, Port );
68. Try {
69. Socket. Receive (packet );
70. String message = new string (packet. getdata (), 0, packet
71. . Getlength ());
72. Showarea. append ("/N" + message );
73. Showarea. setcaretposition (showarea. gettext (). Length ());
74. } Catch (exception e ){
75. }
76. If (stop = true)
77. Break;
78. }
79. }
81. Public static void main (string ARGs []) {
82. New receive ();
83. }
84. }

The idea is clear and easy to understand.