Implementation way is Client0 Client1, Client2 messaging Server forwards the message to others
Server:

 package JChat; 

Import the Java. The awt. Event. An ActionEvent; 
Import the Java. The awt. Event. ActionListener; 
Import the Java. IO. A DataInputStream; 
Import the Java. IO. DataOutputStream; 
import java.io.IOException; 
The import java.net.ServerSocket; 
import java.net.Socket; 
import java.util.Scanner; 

The import javax.mail. Swing. JButton; 
The import javax.mail. Swing. JFrame; 
The import javax.mail. Swing. JTextArea; 
The import javax.mail. Swing. JTextField; 

Public class Server {

Public static void main (String [] args) throws the Exception {

JFrame f=new JFrame (); 
F.s etTitle (" Server "); 

F.s etSize (400, 400); 
F.s etLocation (100, 200); 
F.s etLayout (null); 
F.s etResizable (false); 

JButton b=new JButton (" sent "); 
B.s etBounds (300, 310, 80, 30); 
F.a dd (b); 


Final JTextField tf=new JTextField (); 
Tf. SetBounds (10, 310, 280, 30); 
F.a dd (tf); 

Final JTextArea ta=new JTextArea (); 
Ta. SetBounds (10, 10, 300, 280); 
F.a dd (ta); 

F.s etDefaultCloseOperation (JFrame. EXIT_ON_CLOSE); 
F.s etVisible (true); 

ServerSocket ss2=new ServerSocket (8882); 
System. The out. Println (" listenning on port: 8882 "); 
Final Socket s2=ss2. The accept (); 

ServerSocket ss1=new ServerSocket (8881); 
System. The out. Println (" listenning on port: 8881 "); 
Final Socket s1=ss1. The accept (); 

ServerSocket ss=new ServerSocket (8880); 
System. The out. Println (" listenning on port: 8880 "); 
Final Socket s=ss. The accept (); 

//receive c1 
New Thread () {
Public void the run () {
While (true) {
Try {
A DataInputStream dis=new a DataInputStream (
S1. GetInputStream ()); 
A String of text=dis. ReadUTF (); 
Ta. Append (text + "\ r \ n"); 
Int l=text. The length (); 
If (l<2) {
DataOutputStream DOS=new DataOutputStream (
S.g etOutputStream ()); 
DOS. WriteUTF (text); 
DataOutputStream dos2=new DataOutputStream (
S2. GetOutputStream ()); 
Dos2. WriteUTF (text); 
} 
The else {
If (text. CharAt (l - 2)=='@' & amp; & Text. CharAt (l - 1)=='0') {

DataOutputStream DOS=new DataOutputStream (
S.g etOutputStream ()); 
DOS. WriteUTF (text); 
} 
Else if (text. CharAt (l - 2)=='@' & amp; & Text. CharAt (l - 1)=='2') {
DataOutputStream dos2=new DataOutputStream (
S2. GetOutputStream ()); 
Dos2. WriteUTF (text); 
} 

The else {
DataOutputStream DOS=new DataOutputStream (
S.g etOutputStream ()); 
DOS. WriteUTF (text); 
DataOutputStream dos2=new DataOutputStream (
S2. GetOutputStream ()); 
Dos2. WriteUTF (text); 
} 
} 
} 
The catch (Exception e) {
e.printStackTrace(); 
} 
} 
} 
}; 
} 
} 

Client2 (Client1 and Client0 similar) :

 package JChat; 

Import the Java. The awt. Event. An ActionEvent; 
Import the Java. The awt. Event. ActionListener; 
Import the Java. IO. A DataInputStream; 
Import the Java. IO. DataOutputStream; 
import java.io.IOException; 
The import java.net.ServerSocket; 
import java.net.Socket; 
import java.net.UnknownHostException; 

The import javax.mail. Swing. JButton; 
The import javax.mail. Swing. JFrame; 
The import javax.mail. Swing. JTextArea; 
The import javax.mail. Swing. JTextField; 

Public class Client2 {

Public static void main (String [] args) throws the Exception {

JFrame f=new JFrame (); 
F.s etTitle (" Client2 "); 

F.s etSize (400, 450); 
F.s etLocation (600, 200); 
F.s etLayout (null); 
F.s etResizable (false); 

JButton b=new JButton (" sent "); 
B.s etBounds (300, 310, 80, 30); 
F.a dd (b); 

JButton c=new JButton (" @ client0 "); 
C.s. etBounds (10, 350, 150, 30); 
F.a dd (c); 

JButton c1=new JButton (" @ client1 "); 
C1. SetBounds (200, 350, 150, 30); 
F.a dd (c1); 

Final JTextField tf=new JTextField (); 
Tf. SetBounds (10, 310, 280, 30); 
F.a dd (tf); 

Final JTextArea ta=new JTextArea (); 
Ta. SetBounds (10, 10, 300, 280); 
F.a dd (ta); 

F.s etDefaultCloseOperation (JFrame. EXIT_ON_CLOSE); 
F.s etVisible (true); 

Final Socket s2=new Socket (" 127.0.0.3 ", 8882); 

New Thread () {
Public void the run () {
While (true) {
Try {
A DataInputStream dis=new a DataInputStream (
S2. GetInputStream ()); 
A String of text=dis. ReadUTF (); 
Ta. Append (text + "\ r \ n"); 
} the catch (Exception e) {
e.printStackTrace(); 
} 
} 

} 
}. The start (); 

B.a ddActionListener (new ActionListener () {

@ Override 
Public void actionPerformed (an ActionEvent e) {

String text=tf. The getText (); 
Ta. Append (text + "\ r \ n"); 

Try {
DataOutputStream DOS=new DataOutputStream (
S2. GetOutputStream ()); 
DOS. WriteUTF (text); 
{} the catch (Exception ex) 
ex.printStackTrace(); 
} 

} 
}); 

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