Basics of Socket Programming in Java
Simple Client Program
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import java.util.*;
import java.net.*;
import java.io.*;
public class client
{
public static void main(String[] args) throws Exception
{
Socket s = new Socket("localhost", 12345);
DataInputStream input = new DataInputStream(s.getInputStream());
DataOutputStream output = new DataOutputStream(s.getOutputStream());
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
boolean x = true;
while(x)
{
System.out.println("enter to send ");
String message = reader.readLine();
if(message.equals("stop"))
x = false;
output.writeUTF(message);
String response = input.readUTF();
System.out.println("server says --- " + response);
}
s.close();
}
}
Simple Server Program
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import java.net.*;
import java.util.*;
import java.io.*;
public class server
{
public static void main(String[] args) throws Exception
{
ServerSocket ss = new ServerSocket(12345);
Socket s = ss.accept();
DataInputStream input = new DataInputStream(s.getInputStream());
DataOutputStream output = new DataOutputStream(s.getOutputStream());
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
boolean x = true;
while(x)
{
String message = input.readUTF();
System.out.println("client says --- " + message);
if(message.equals("stop"))
x = false;
if(x)
System.out.println("enter to send ");
String respond = x?reader.readLine():"END_SESSION_!";
output.writeUTF(respond);
}
s.close();
ss.close();
}
}
Multi-threaded Server
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import java.util.*;
import java.net.*;
import java.io.*;
public class multithreadserver implements Runnable
{
Socket client;
multithreadserver(Socket client)
{
this.client = client;
}
public static void main(String[] args) throws Exception
{
ServerSocket ss = new ServerSocket(12345);
while(true)
{
Socket sock = ss.accept();
new Thread(new multithreadserver(sock)).start();
}
}
public void run()
{
try
{
DataInputStream input = new DataInputStream(client.getInputStream());
DataOutputStream output = new DataOutputStream(client.getOutputStream());
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
InetAddress addr = client.getInetAddress();
boolean x = true;
while(x)
{
String message = input.readUTF();
System.out.println(addr.getHostAddress() + "says --- " + message);
if(message.equals("stop"))
x = false;
if(x)
System.out.println("enter to send to " + addr.getHostAddress());
String respond = x?reader.readLine():"END_SESSION_!";
output.writeUTF(respond);
}
client.close();
}
catch(IOException e)
{
e.printStackTrace();
}
}
}
Banner Grabbing - Get Request
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import java.util.*;
import java.net.*;
import java.io.*;
public class get_request
{
public static void main(String[] args) throws Exception
{
InetAddress addr = InetAddress.getByName("www.avajava.com");
Socket client = new Socket(addr, 80);
PrintWriter output = new PrintWriter(client.getOutputStream());
BufferedReader input = new BufferedReader(new InputStreamReader(client.getInputStream()));
output.println("GET / HTTP/1.1");
output.println("Host: www.avajava.com");
output.println();
output.flush();
String line;
while((line = input.readLine())!=null)
{
System.out.println(line);
}
}
}
Download Image using Get Request
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import java.util.*;
import java.net.*;
import java.io.*;
public class download_image
{
public static void main(String[] args) throws Exception
{
InetAddress addr = InetAddress.getByName("www.bits-pilani.ac.in");
Socket client = new Socket(addr, 80);
PrintWriter output = new PrintWriter(client.getOutputStream());
DataInputStream input = new DataInputStream(client.getInputStream());
output.println("GET /Uploads/Campus/BITS_Dubai_campus_logo.gif HTTP/1.1");
output.println("Host: www.bits-pilani.ac.in");
output.println();
output.flush();
FileOutputStream img = new FileOutputStream(new File("img.gif"));
byte[] rec = new byte[2048];
boolean eohfound = false;
int count;
while((count=input.read(rec))!=-1)
{
int start = 0;
if(!eohfound)
{
String yu = new String(rec, 0, count);
int index = yu.indexOf("\\r\\n\\r\\n");
if(index!=-1)
{
start = index + 4;
count = count - index - 4;
eohfound = true;
}
else
count = 0;
}
img.write(rec, start, count);
}
img.close();
input.close();
output.close();
client.close();
}
}
Banner Grabbing - HttpURLConnection
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import java.util.*;
import java.net.*;
import java.io.*;
public class httprequest
{
public static void main(String[] args) throws Exception
{
String url = "<http://www.java2s.com>";
URL object = new URL(url);
HttpURLConnection connection = (HttpURLConnection)object.openConnection();
connection.setRequestMethod("GET");
BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
String line;
while((line=in.readLine())!=null)
{
System.out.println(line);
System.out.flush();
}
}
}
Download Image using HttpURLConnection
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import java.util.*;
import java.net.*;
import java.io.*;
public class httprequest_download
{
public static void main(String[] args) throws Exception
{
URL object = new URL("<http://bits-pilani.ac.in/Uploads/Campus/BITS_Dubai_campus_logo.gif>");
HttpURLConnection connection = (HttpURLConnection)object.openConnection();
connection.setRequestMethod("GET");
FileOutputStream webpage = new FileOutputStream(new File("img.gif"));
DataInputStream in = new DataInputStream(connection.getInputStream());
int count;
byte[] buffer = new byte[2048];
while((count = in.read(buffer))!=-1)
{
webpage.write(buffer, 0, count);
webpage.flush();
}
in.close();
webpage.close();
}
}
This post is licensed under CC BY 4.0 by the author.