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Connection time out in Java Server-Client

I have a small program where a Server-Client program is getting connected on the same network, but the same program shows a connection time out error in the client program. I have connected the two systems using LAN cable.
Server
import java.io.IOException;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Date;
public class DateServer {
public static void main(String[] args) throws IOException {
ServerSocket listener = new ServerSocket(9090);
try {
while (true) {
Socket socket = listener.accept();
try {
PrintWriter out =
new PrintWriter(socket.getOutputStream(), true);
out.println(new Date().toString());
} finally {
socket.close();
}
}
} finally {
listener.close();
}
}
}
Client
import java.io.BufferedReader;
import java.io.IOException ;
import java.io.InputStreamReader;
import java.net.Socket;
import javax.swing.JOptionPane;
public class DateClient {
public static void main(String[] args) throws IOException {
String serverAddress = JOptionPane.showInputDialog(
"Enter IP Address of a machine that is\n" +
"running the date service on port 9090:");
Socket s = new Socket(serverAddress, 9090);
BufferedReader input =
new BufferedReader(new InputStreamReader(s.getInputStream()));
String answer = input.readLine();
JOptionPane.showMessageDialog(null, answer);
System.exit(0);
}
}

Since the code runs on the same computer, three possibilities come to my mind:
The problem can be either your firewall/access to port rights or having IP addresses as mentioned by other fellows.
You are setting the IP address of the server wrong.
The IP address of the server does not lie on the subnet mask of your network. If you have literaly connected the two computers with a cable (no routers in the middle) you probably haven't setup a DHCP, i.e., your ip addresses should be manually selected. If the ip is selected randomly, chances are your client computer can't find the server computer. try manually setting the ip addresses of both computers to an invalid address within the same subnet mask range and see if it works.
For example set the following addresses:
client IP: 192.168.1.10
subnetmask: 255.255.255.0
server IP: 192.168.1.11
subnetmask: 255.255.255.0

Connecting the two systems with a LAN cable is not sufficient. You have to ensure they have distinct IP addresses, are both in the same IP subnet, and/or have appropriate IP routing tables defined. More typically you would connect both via a router.

Get all the Up ip in the local network -java

For the Java project i need to scan the list of ip connected to the same local network via wlan or eth0 or anything. I need to get the list of ip address that are up in the local network.
I tried
InetAddress localHost = Inet4Address.getLocalHost();
NetworkInterface networkInterface = NetworkInterface.getByInetAddress(localHost);
for (InterfaceAddress address : networkInterface.getInterfaceAddresses())
{
System.out.println(address.getNetworkPrefixLength());
}
But it gives
Exception in thread "main" java.lang.NullPointerException
at com.Server.Subnet.main(Subnet.java:17)
I think i need to follow these steps.
Get the subnet address of the network that i connected
Scan all the ip address in the subnet mask
List the ip address that are up
Can you give me the right implementation way

Follow these directions
-- get your system IP
-- get your subnet mask.
-- As per your subnet mask, get the list of possible IP addresses in your subnet.&
-- Now, one by one ping them. (you can use system ping command with java)
-- check ping response, then you can decide whether the host is up or not.

I tried this program to find all the up ip in the subnet of the system connected.
package com.Server;
import java.io.IOException;
import java.net.Inet4Address;
import java.net.InetAddress;
import java.net.InterfaceAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.net.UnknownHostException;
import java.util.Enumeration;
public class Subnet
{
public void Subnet() throws UnknownHostException, SocketException
{
Enumeration e = NetworkInterface.getNetworkInterfaces();
while(e.hasMoreElements())
{
NetworkInterface n = (NetworkInterface) e.nextElement();
Enumeration ee = n.getInetAddresses();
while (ee.hasMoreElements())
{
InetAddress i = (InetAddress) ee.nextElement();
String ip = i.getHostAddress();
String sip = ip.substring(0, ip.indexOf('.',ip.indexOf('.',ip.indexOf('.')+1) + 1) + 1);
try {
for(int it=1;it<=255;it++)
{
String ipToTest = sip+it;
boolean online = InetAddress.getByName(itToTest).isReachable(100);
if (online) {
System.out.println(ipToTest+" is online");
}
}
} catch (IOException e1) {
System.out.println(sip);
}
}
}
}
}

Accessing serial com port in windows8 through java

I want access serial com port in windows 8 but I'm unable to get com port using java but com port is showing in "Device Manager". Please do the needfull. Is any additional setting is required ?
I'm using the following code in windows8.
import java.util.Enumeration;
import javax.comm.CommPortIdentifier;
import javax.comm.SerialPortEvent;
import javax.comm.SerialPortEventListener;
public class SerialPortReading implements SerialPortEventListener {
public static void main(String[] args) {
//
// Get an enumeration of all ports known to JavaComm
//
Enumeration portIdentifiers = CommPortIdentifier.getPortIdentifiers();
CommPortIdentifier portId = null; // will be set if port found
while (portIdentifiers.hasMoreElements())
{
CommPortIdentifier pid = (CommPortIdentifier) portIdentifiers.nextElement();
if(pid.getPortType() == CommPortIdentifier.PORT_SERIAL)
{
System.out.println(pid.getName());
}
}
#Override
public void serialEvent(SerialPortEvent se) {
System.out.println("ok");
}
}

Java Communications API does not support Windows any more: Oracle Download Page. Use another library for example:
JSerialComm

IP Address in a wired /wireless LAN using java

I am working on a java server-client app that transfers file btw each oda within a wired or wireless LAN, my problem now is how to detect the IP address of the client computer and the server computer in a wireless or wired LAN. Bottom-line: how to i use java code to detect the ip address of a computer in a wired or wireless LAN connection btw two computers.

Maybe jgroups can help you: http://www.jgroups.org

import java.io.*;
import java.net.*;
import java.util.*;
import static java.lang.System.out;
public class ListNets {
public static void main(String args[]) throws SocketException, UnknownHostException {
System.out.println(System.getProperty("os.name"));
Enumeration<NetworkInterface> nets = NetworkInterface.getNetworkInterfaces();
for (NetworkInterface netint : Collections.list(nets))
if (netint.getName().equals("wlan0") || netint.getName().equals("en0")) {
displayInterfaceInformation(netint);
}
}
static void displayInterfaceInformation(NetworkInterface netint) throws SocketException {
out.printf("Display name: %s\n", netint.getDisplayName());
out.printf("Name: %s\n", netint.getName());
Enumeration<InetAddress> inetAddresses = netint.getInetAddresses();
for (InetAddress inetAddress : Collections.list(inetAddresses)) {
out.printf("InetAddress: %s\n", inetAddress);
}
out.printf("\n");
}
}

Detecting Windows/IE proxy setting using Java

I need to automatically detect if a user requires a proxy to access the internet. Is there a way for a Java application to read the systems proxy setting?
Thanks,
Jimmy

Java SE 1.5 provides ProxySelector class to detect the proxy settings. If there is a Direct connection to Internet the Proxy type will be DIRECT else it will return the host and port.
Example below illustrates this functionality:
import java.net.InetSocketAddress;
import java.net.Proxy;
import java.net.ProxySelector;
import java.net.URI;
import java.util.Iterator;
import java.util.List;
public class TestProxy {
public static void main(String[] args) {
try {
System.setProperty("java.net.useSystemProxies","true");
List<Proxy> l = ProxySelector.getDefault().select(
new URI("http://www.yahoo.com/"));
for (Iterator<Proxy> iter = l.iterator(); iter.hasNext(); ) {
Proxy proxy = iter.next();
System.out.println("proxy hostname : " + proxy.type());
InetSocketAddress addr = (InetSocketAddress)proxy.address();
if(addr == null) {
System.out.println("No Proxy");
} else {
System.out.println("proxy hostname : " + addr.getHostName());
System.out.println("proxy port : " + addr.getPort());
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}

The other, accepted, answer is undoubtedly excellent and correct but I thought I would add something here...
If you are on a machine that is configured with "auto detect proxy settings", which I believe is called PAC, the code to detect the proxy in the answer using the Java gubbins will not work (it will think it is a "direct" connection).
There is a library called proxy vole (new BSD license I think), however, that you can use instead so here's the other answer's code slightly modified to use that:
public class testProxy {
public static void main(String[] args) {
try {
System.setProperty("java.net.useSystemProxies","true");
// Use proxy vole to find the default proxy
ProxySearch ps = ProxySearch.getDefaultProxySearch();
ps.setPacCacheSettings(32, 1000*60*5);
List l = ps.getProxySelector().select(
new URI("http://www.yahoo.com/"));
//... Now just do what the original did ...
for (Iterator iter = l.iterator(); iter.hasNext(); ) {
Proxy proxy = (Proxy) iter.next();
System.out.println("proxy hostname : " + proxy.type());
InetSocketAddress addr = (InetSocketAddress)
proxy.address();
if(addr == null) {
System.out.println("No Proxy");
} else {
System.out.println("proxy hostname : " +
addr.getHostName());
System.out.println("proxy port : " +
addr.getPort());
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
It needs these imports:
import java.net.InetSocketAddress;
import java.net.Proxy;
import java.net.URI;
import java.util.Iterator;
import java.util.List;
import com.btr.proxy.search.ProxySearch;
Oh, and there're usage examples for proxy vole here.