De bai:Chuoi co ban client-UDP

//UDPClient.java import java.io.*; import java.net.*; class UDPClient { public static void main(String[] args) { //Khai bao bien DatagramSocket cl=null; byte[] inBuff,outBuff;//Bo dem nhap /xuat DatagramPacket inData,outData;//Bien Goi tin nhan gui String ipserver="localhost"; int pserver=3456; String s="Hello World!"; try{ //Tao so cket voi so hieu cong nao do cl=new DatagramSocket(); //Tao goi tin gui //- Cap bo nho cho outData va gan du lieu cho no outBuff=s.getBytes(); //- Tao goi tin gui outData=new DatagramPacket(outBuff,outBuff.length, InetAddress.getByName(ipserver),pserver); //Gui goi tin cl.send(outData); //Tao goi tin nhan //- Cap bo nho cho inBuff inBuff=new byte[516]; //- Tao goi tin nhan inData=new DatagramPacket(inBuff,inBuff.length); //Nhan goi tin cl.receive(inData); //Tach du lieu tu goi tin va chuyen thanh chuoi s=new String(inData.getData()); System.out.println("Chuoi tra ve tu server:"+s); //Ket thuc chuong trinh inBuff=outBuff=null; inData=outData=null; cl.close(); } catch(IOException e) { System.out.println(e); } } }

//UDPServer.java import java.io.*; import java.net.*; class UDPServer { public static void main(String[] args) { //Khai bao bien DatagramSocket svr=null; byte[] inBuff,outBuff;//Bo dem nhap /xuat DatagramPacket inData,outData;//Bien Goi tin nhan gui int pserver=3456; int pclient; InetAddress addrclient; String s; try{ //Tao so cket voi so hieu cong xac dinh svr=new DatagramSocket(pserver); //Tao goi tin nhan //- Cap bo nho cho inBuff inBuff=new byte[516]; //- Tao goi tin nhan inData=new DatagramPacket(inBuff,inBuff.length); //Nhan goi tin svr.receive(inData); //Lay so cong cua client pclient=inData.getPort(); //lay dia chi client addrclient=inData.getAddress(); //Tach du lieu tu goi tin va chuyen thanh chuoi s=new String(inData.getData()); System.out.println("Name:"+addrclient.getHostName()+ ",IP:"+addrclient.getHostAddress()+",Port:"+pclient+",Data:"+s); s=s.toUpperCase(); //Tao goi tin gui //- Cap bo nho cho outData va gan du lieu cho no outBuff=s.getBytes(); //- Tao goi tin gui outData=new DatagramPacket(outBuff,outBuff.length, addrclient,pclient); //Gui goi tin svr.send(outData);//Ket thuc chuong trinh inBuff=outBuff=null; inData=outData=null; svr.close(); } catch(IOException e) { System.out.println(e); } } }