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LP TRNH NG DNG UDP SOCKET TRN JAVA

Mc tiu:

Sau bi thc hnh ny, sinh vin c th:

- Hiu c m hnh hot ng chung ca ng dng mng trn giao thc UDP.- Lp trnh ng dng mng vi UDP socket trn ngn ngJava.

Ni dung chnh:

-

M hnh hot ng giao thc UDP- Mt shm c bn ca lp DatagramSocket.- Minh ha ng dng mng n gin sdng DatagramSocket.

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1.

M hnh hot ng giao thc UDP (User Datagram Protocol)

- Khi xy dng mt ng dng mng, ta cn thc hin cc bc sau:

o Xc nh kin trc mng: Client-Server hay Peer-to-Peer.

o

Giao thc c sdng tn Transport: TCP, UDP.o Cc port sdng Client v Server.

o Giao thc tn ng dng khi trao i dliu.

o Lp trnh.

- Cc phn di y strnh by cc bc c bn xy dng mt ng dng mng

theo kin trc Client-Server sdng giao thc UDP.

- C hai giao thc chnh c dng truyn ti d liu trong TCP/IP l TCP v

UDP.

- Vi ng dng mng c thit ktheo m hnh ca giao thc UDP thun ty, bn

gi khng c c chm bo tn tin cy ca dliu c truyn ti, ngha

l dliu c truyn c thbmt, sai ni dung hoc thtni dung nhn c

so vi ni dung cn gi sbo ln.

- Tuy nhin, UDP c dng trong cc ng dng yu cu thi gian thc nh truyn

ti Video, Audio, v khnng truyn ti nhanh ca n.

-

S tng tc gia Client v Server theo giao thc UDP nh m hnh sau:

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ClientClient Server

Create

Socket

Create

Socket

Bind

CloseClose

Send to

Receive

fromSend to

Receive

from

To socket lng ngheTo socket giao tip

Kt buc vo a ch IPv port

Gi d liu n client

tham s cn truyn vol a ch IP v port mclient ang s dng

Gi d liu n servertham s cn truyn vol a ch IP v port mserver ang lng nghe

Nhn d liu t Client

Nhn d liu t Server

ng kt ni

2. Lp trnh UDP socket trn Java vi lp DatagramSocket:

-

DatagramSocket l lp h tr lp trnh ng dng UDP socket trn Java, phnny sgii thiu mt sphng thc c bn c thxy dng c mt ng

dng UDP socket.

a.

To DatagramSocket:

Public DatagramSocket()

Throws SocketException

o Khi to UDP socket v kt buc n vo mt trong nhng port cn trngca hthng.

Public DatagramSocket( int port)

Throws SocketException

o Khi to UDP socket v kt buc n vo mt port cthc chra.

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b.

Kt buc a chcho DatagramSocket

Public void bind ( SocketAddress addr)

Throws SocketException

o

Kt buc DatagramSocket vo mt a chcth(IP v port)

c.

Gi v nhn dliu vi DatagramSocket

DatagramSocket sdng lp DatagramPacket gi v nhn cc gi tin.

- Nhn dliu:

Public DatagramPacket ( byte []buf, int length)

o Khi to 1 DatagramPacket dng nhn 1 packet c di l length,

lengthphi nhhn hoc bng buf.length

o Buf: vng nhm dng lu dliu sp nhn.

o Length: slng byte sc c.

Public void Receive (DatagramPacket p)

Throws IOException

o

Thc hin nhn vpacket tDatagramSocket, khi hm ny c gi thnhcng, buffer ca DatagramPacket schni dung dliu nhn c. ng

thi DatagramPacket cn cha thng tin va chIP v port ca bn gi.

o Phng thc ny khi gi sbBLOCKcho n khi c 1 DatagramPacket

c nhn.

- Gi dliu:

Public DatagramPacket (byte []buf, int length, SocketAddress address)

Throws SocketException

o Khi to 1 DatagramPacket gi 1 packet c di l lengthn cng c

shiu port trn host cthc chra trong address.

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Public void send ( DatagramPacket p)Throws IOException

o Gi DatagramPacket n host nhn. DatagramPacket chd liu cn gi,

di dliu, a chIP v shiu port ca host snhn.

- Mt sphng thc htrkhc ca lp DatagramPacket:

Public InetAddress getAddress()

o Trva chIP ca host gi packet hoc host snhn packet.

Public int getPort()

o

Trvgi trport ca host gi packet hoc host m packet sc gin.

Public byte[] getData()

o Trvni dung dliu trong DatagramPacket

Public int getLength()

o

Trvdi ca dliu trong DatagramPacket

d.

ng DatagramSocket :

Public void Close()

3. Minh ha ng dng mng n gin sdng DatagramSocket

a.

bi:

Vit mt ng dng mng trn giao thc UDP h tr chat tun t gia Client

Server theo thtClient Server Client Server Client Server bng

Console. Qu trnh chat skt thc khi mt trong hai bn g Exit.

o

Xc nh kin trc mng: CLIENTSERVER

o Giao thc sdng tn transport: UDP

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o Port lng nghe pha server 1234

o Giao thc tng ng dng khi trao i dliu gia client-server

b.

Chng trnh(tham kho source code km theo)

Ti liu tham kho:

http://docs.oracle.com/javase/1.4.2/docs/api/java/net/DatagramSocket.html

http://docs.oracle.com/javase/1.4.2/docs/api/java/net/DatagramPacket.html

http://docs.oracle.com/javase/1.4.2/docs/api/java/net/DatagramSocket.htmlhttp://docs.oracle.com/javase/1.4.2/docs/api/java/net/DatagramSocket.htmlhttp://docs.oracle.com/javase/1.4.2/docs/api/java/net/DatagramPacket.htmlhttp://docs.oracle.com/javase/1.4.2/docs/api/java/net/DatagramPacket.htmlhttp://docs.oracle.com/javase/1.4.2/docs/api/java/net/DatagramPacket.htmlhttp://docs.oracle.com/javase/1.4.2/docs/api/java/net/DatagramSocket.html