TCP Chat

Codes for Client end. Save the file as Client.java
import java.io.*; import .*; class Client { public static void main(String args[ ]) { try { System.out.print("Client connecting to Server.... \n"); Socket skt = new Socket("localhost", 1234); BufferedReader in = new BufferedReader(new InputStreamReader(skt.getInputStream())); System.out.print("Connected to Server.....\n"); System.out.print("Received string from Server: '\n"); while (!in.ready()) { } System.out.println(in.readLine()); System.out.print("'\n"); in.close(); } catch(Exception e) { System.out.print("Client Can't find the Server!\n"); } } }
• There are a total of 65535 ports in a computer. • These ports are classified into three range.
Well Known Port Number
Open Ports on Windows XP
• To see a list of open ports on Windows XP type those following commands in command prompt.
The data packet must include both the IP address and a port number, i.e. IP Address : Port Number
Computer Port Number
Most well known services (e.g. HTTP, FTP, Telnet, SMTP, etc..) are running in this range
Stream socket
• In computer networking, a stream socket is a type of internet socket which provides a connection-oriented, sequenced, and unduplicated flow of data, with well-defined mechanisms for creating and destroying connections and for detecting errors.
Java Program TCP Sockets
Santosh Kumar Sahu
Master in Computer Application Software School, Nanchang University Jiangxi, China ( QQ : 860397288, Email : santoshkumarsahu@aols
• ServerSocket srvr = new ServerSocket(1234);
• // Set the server to port no 1234 • Socket skt = srvr.accept(); • //skt "warp tunnel" through which we can communicate with client • //waits until a client attempts to connect to the server by socket
Run the Server and Client
When the Server is on State and Client in off state
When the Server is off State and Client in on state
When the Server is on State and Client in on state
• PrintWriter out = new PrintWriter(skt.getOutputStream(), true);
• // skt.getOutputStream() returns the output stream through which the server can talk to the client
Codes for Server end. Save the file as Server.java
import java.io.*; //handling input output operations import .*; // Classes supporting TCP/IP based client-server connections public class Server { public static void main(String args[ ]) { String data = "Hello Client I am Server, Have you received my Data"; try { System.out.print("Server waiting for client!\n"); ServerSocket srvr = new ServerSocket(1234); Socket skt = srvr.accept(); System.out.print("Client has connected to Server!\n"); PrintWriter out = new PrintWriter(skt.getOutputStream(), true); System.out.print("Sending string: '" + data + "'\n"); out.print(data); out.close(); skt.close(); srvr.close(); } catch(Exception e) { System.out.print("Server Can't find the client!\n"); } } }
Explain the codes
try { body-code } catch (exception-classname variable-name) { handler-code } • The try/catch statement encloses some code and is used to handle errors and exceptions that might occur in that code.
What is computer port
• A port may be considered as the “communication point” of a computer. • As we know, there are many applications (e.g. web server, FTP server, mail server, etc..) running in a computer. • Each application will occupy a specific port. • Therefore a computer allow many applications running in the same time without interfere or confict with each others.
• netstat -ano • netstat -anobv • tasklist /svc
Java Program TCP Sockets
Concept of the program
• In order to initiate a TCP session, a server (Provider) and a client (Requester) are required. • A server Program is set up to listen at a given port. • The server waits and does nothing until a client attempts to connect that port. • If everything goes fine, the connection is successful and both the server and client by the Socket. • Server program creates a Out going Stream to send data through the socket. • Client program creates an In coming stream to receive data through the socket • All communication is done via these streams between the Server and Client Program
• out.print(data); • // sends the data (stored in the variable data) to the client • out.close(); // Close the out stream • skt.close(); // Close the socket • srvr.close(); // Close the Server