I am trying to create a simple web proxy app using Java(without using the HTTPUrlConnection class).
I have so far managed to successfully have my server listen on port 10000, and then accept a client connection when I enter a URL into my browser.
I now require my proxy to forward the HTTP request from the browser to the actual web server(the URL which I typed into the browser).
However, I am getting a java.net.UnknownHostException: when attempting to create a socket connection between my proxy and the web server. Does anyone know what may be causing this issue?
Below is the output showing the error aswell as the complete code aswell. Any help is very much appreciated!
Starting the socket server at port:10000
Listening.....
Socket[addr=/127.0.0.1,port=64099,localport=10000]has connected
URL IS http://www.hotmail.com
Can't connect
java.net.UnknownHostException: http://www.hotmail.com
import java.net.*;
import java.io.*;
public class Proxy {
private ServerSocket serverSocket;
private int port;
public Proxy(int port) {
this.port = port; }
public static void main(String[] args) {
int port = 10000;
try {
// initialize the proxy
Proxy proxy = new Proxy(port);
proxy.start();
}
catch (IOException e) {
e.printStackTrace();
}
}
public void start() throws IOException {
System.out.println("Starting the socket server at port:" + port);
serverSocket = new ServerSocket(port);
//Listen for client connection
System.out.println("Listening.....");
Socket client = serverSocket.accept();
//A client has connected to this server
verifyClient(client);
}
private void verifyClient(Socket client) throws IOException {
System.out.println(client + "has connected");
BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream()));
//Parse the HTTP request from the browser and find the URL
String request;
while ((request = in.readLine()) != null) {
if (request.contains("http://")){
StringBuilder sb = new StringBuilder(request);
sb.delete(0,4);
sb.delete(sb.length()-9,sb.length());
makeConnection(sb.toString());
break;}
in.close();
}
}
private void makeConnection(String url) throws IOException{
//Establish connection between proxy & web server on socket
try {
InetAddress addr;
URL aURL = new URL(url);
System.out.println("URL IS " + aURL.toString());
Socket server = new Socket(urlString,80);
addr = server.getInetAddress();
System.out.println("IP is: " + addr);
System.out.println("Connected to " + addr);
server.close();
}
catch (IOException e) {
System.out.println("Can't connect");
System.out.println(e);
}
}
From your update, it seems like you are trying to create a socket connection to "http://www.hotmail.com". This should just be www.hotmail.com. The "http://" before this is a problem.
Related
I'm having the following TCP client code:
public static void register(InetAddress ip, int port, String name) {
try {
Socket clientSocket = new Socket(ip, port);
send("reg:" + name);
} catch (Exception e) {
e.printStackTrace();
}
}
public static void send(String str) {
try {
String sentence = str;
DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream());
outToServer.writeBytes(sentence);
} catch (IOException e) {
Log.e("CONNECT", e.getMessage());
}
}
They both are called in onClicks and i know that for sure.
I also have the following Server code:
public static void main(String argv[]) throws Exception {
String clientSentence;
ServerSocket welcomeSocket = new ServerSocket(9876);
while (true) {
Socket connectionSocket = welcomeSocket.accept();
BufferedReader inFromClient = new BufferedReader(
new InputStreamReader(connectionSocket.getInputStream()));
DataOutputStream outToClient = new DataOutputStream(
connectionSocket.getOutputStream());
clientSentence = inFromClient.readLine();
System.out.println("Received: " + clientSentence);
outToClient.writeBytes("msg: Hello! kalin pedro");
}
}
When trying to send data to the server i don't get an exception, i also know that I'm connected to it because the application is crashing when i terminate the server application. The problem is that the server doesn't receive anything until i terminate the client application. Everything that i have tried to send until that moment is all received from the server at once. I looked at the network activity tab provided by Android Studio and there is a change when sending data, the server just doesn't receive it(or at least i don't see it receive it) until i terminate the client application.
I just recently found the ServerSocket and Socket class found in the Java library and so I wanted to make a simple messaging app. The purpose of the app is to be able to communicate with someone on a different network than mine (I am the server side and have my own client side).
Here is the Messenger_Server.java's connecting method
public static void main (String [] args)throws IOException{
InetAddress ip;
try{
final int PORT = 444;
ip = InetAddress.getLocalHost();
ServerSocket server = new ServerSocket(PORT);
System.out.println("Waiting for clients...");
System.out.println(server.getInetAddress() + " " + ip.getHostAddress());
while(true){
Socket sock = server.accept();
connectionArray.add(sock);
System.out.println("Client connected from " + sock.getLocalAddress().getHostName());
addUserName(sock);
Messenger_Server_Return chat = new Messenger_Server_Return(sock);
Thread X = new Thread(chat);
X.start();
}
} catch(Exception e) {
e.printStackTrace();
}
}
Here is the client's connecting method from Messenger_Client.java
public static void connect(){
try{
final int PORT = 444;
// the ip below is the one i get as my ipv4
Socket sock = new Socket ("10.122.***.***",PORT);
System.out.println("you be connected to: " + InetAddress.getByAddress(InetAddress.getLocalHost().getAddress()));
chatClient = new Messenger_Client(sock);
PrintWriter out = new PrintWriter(sock.getOutputStream());
out.println(userName);
out.flush();
Thread X = new Thread(chatClient);
X.start();
}catch (Exception X){
X.printStackTrace();
JOptionPane.showMessageDialog(null, "Server not responding.");
System.exit(0);
}
}
So I gave the client side of the program to my friend and he said the host could not be found. Which IP should I use so my friend can connect to my ServerSocket, and could there be anything limiting my friend from connecting to me?
I'm working on a program where multiple clients need to interact with a remote server.
I've tested it locally and everything's ok (sort of, more on that later), but I can't understand how to set a remote IP.
I read Socket's API and also InetAddress' API. Is this the right way to do it? How does Java deal with IPs? There are not just simple Strings as on the localhost case, am I right?
This is my code:
Client:
public class Client {
final String HOST = "localhost";
final int PORT = 5000;
Socket sc;
DataOutputStream message;
DataInputStream istream;
public void initClient() {
try {
sc = new Socket(HOST, PORT);
message = new DataOutputStream(sc.getOutputStream());
message.writeUTF("test");
sc.close();
} catch (Exception e) {
System.out.println("Error: " + e.getMessage());
}
}
}
Server:
public class Server {
final int PORT = 5000;
ServerSocket sc;
Socket so;
DataOutputStream ostream;
String incomingMessage;
public void initServer() {
try {
sc = new ServerSocket(PORT);
} catch (IOException ex) {
System.out.println("Error: " + ex.getMessage());
}
BufferedReader input;
while(true){
try {
so = new Socket();
System.out.println("Waiting for clients...");
so = sc.accept();
System.out.println("A client has connected.");
input = new BufferedReader(new InputStreamReader(so.getInputStream()));
ostream = new DataOutputStream(so.getOutputStream());
System.out.println("Confirming connection...");
ostream.writeUTF("Successful connection.");
incomingMessage = input.readLine();
System.out.println(incomingMessage);
sc.close();
} catch (Exception e) {
System.out.println("Error: " + e.getMessage());
}
}
}
}
Also, I'm dealing with some troubles on my local tests.
First of all, some times I get the following result:
Waiting for clients...
A client has connected.
Confirming connection...
Error: Software caused connection abort: recv failed
Though some other times it works just fine. Well, that first connection at least.
Last question:
When I try to send a message from the server to the client, the program enters in an infite loop and need to be closed manually. I'm adding this to the code to do so:
fromServerToClient = new BufferedReader(new InputStreamReader(sc.getInputStream()));
text = fromServerToClient.readLine();
System.out.println(text);
Am I doing it right?
Thanks.
Instead of using
String host = "localhost";
you can use something like
String host = "www.ibm.com";
or
String host = "8.8.8.8";
this is how you would usually implement a Server:
class DateServer {
public static void main(String[] args) throws java.io.IOException {
ServerSocket s = new ServerSocket(5000);
while (true) {
Socket incoming = s.accept();
PrintWriter toClient =
new PrintWriter(incoming.getOutputStream());
toClient.println(new Date());
toClient.flush();
incoming.close();
}
}
}
And following would be As Client:
import java.util.Scanner;
import java.net.Socket;
class DateClient {
public static void main(String[] args) throws java.io.IOException
{
String host = args[0];
int port = Integer.parseInt(args[1]);
Socket server = new Socket(host, port);
Scanner scan = new Scanner( server.getInputStream() );
System.out.println(scan.nextLine());
}
}
You should consider doing this in threads. Right now multiple users can't connect to the server at once. This means that they have to queue for connection to the server resulting in very poor performance.
Normally you receive the client and instantiate a new thread to handle the clients request. I only have exampls in C# so i won't bother you with that, but you can easily find examples on google.
eg.
http://www.kieser.net/linux/java_server.html
i am creating a simple client/server app
and was able to connect multiple clients to single server.
i referred to this link client/server simple app demo
my problem is that now,i want to return some response from server to client
based on its client/ip address.
eg. if 192.123.1.1 connects the response should be xml
if 192.123.1.2 connects the response should be json.
is it possible to do?? any help will be appreciated
here is my simple server code:
public class ChatServer implements Runnable
{
private ServerSocket server = null;
private Thread thread = null;
private ChatServerThread client = null;
public ChatServer(int port)
{ try
{ System.out.println("Binding to port " + port + ", please wait ...");
server = new ServerSocket(port);
System.out.println("Server started: " + server);
start();
}
catch(IOException ioe)
{ System.out.println(ioe); }
}
public void run()
{ while (thread != null)
{ try
{ System.out.println("Waiting for a client ...");
addThread(server.accept());
}
catch(IOException ie)
{ System.out.println("Acceptance Error: " + ie); }
}
}
public void addThread(Socket socket)
{ System.out.println("Client accepted: " + socket);
client = new ChatServerThread(this, socket);
try
{ client.open();
client.start();
}
catch(IOException ioe)
{ System.out.println("Error opening thread: " + ioe); }
}
public void start()
public void stop()
public static void main(String args[])
I think instead of ip check the client should ask for the type of data they want. I am not sure why you require a check on ip. But in future if you all more clients then you have to change the server code every time. Better to define the format in the client so that client can ask for data of specific type.
Not very sure about your requirement.
There is an API call Socket.getRemoteSocketAddress().toString() to get the caller IP
Socket clientSocket =server.accept();
System.out.println(" client ip address =" +clientSocket.getRemoteSocketAddress().toString());
-- once you obtained clientSocket, use below sample to write back
Socket clientSocket =server.accept();
String returMessage ="Hello from Server ";
if (clientSocket.getRemoteSocketAddress().toString().equals("192.168.1.3")){
returMessage=returMessage +" welcome browser";
}
else if(clientSocket.getRemoteSocketAddress().toString().equals("192.168.1.4")){
returMessage=returMessage +" welcome tablet";
}
OutputStream os = clientSocket .getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os);
BufferedWriter bw = new BufferedWriter(osw);
bw.write(returMessage);
System.out.println("Message sent to the client is "+returMessage);
bw.flush();
-- To read from client
InputStream is = clientSocket.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String data = br.readLine();
System.out.println("Message received from client is "+data);
if("send_players".equals(data)){ // reading data you would need to finetune
//write playerlist
}
I have a client and a server. The client binds a socket on a specific port, the server sends back a new port to the client and the client should bind a new socket on the new port number.
From the main server thread, I start a thread that sends a message to the client once the server is ready and is listening to the new port, so that the client can attempt to connect to the new port. The pipe from the child thread is not sending the message to the client.
So both client and server just freeze, it seems like a deadlock, but im not sure. This line of code in the client: System.out.println("FROM SERVER: " + inMsg_rport); is not executing.
Server Code:
class server
{
public static void main(String argv[]) throws Exception
{
String newPort;
ServerSocket serverSocket = null;
Socket clientSocket = null;
try
{
serverSocket = new ServerSocket(5555);
clientSocket = serverSocket.accept();
DataOutputStream serverOut =
new DataOutputStream(clientSocket.getOutputStream());
int r_port = 5556;
Thread appThread = new Thread(new serverApp(serverOut, r_port));
appThread.start();
}
catch(IOException e)
{
System.out.println(e);
}
}
static class serverApp implements Runnable
{
DataOutputStream serverOut;
int nPort;
public serverApp(DataOutputStream servO, int r_port)
{
this.serverOut = servO;
this.nPort = r_port;
}
#Override
public void run()
{
ServerSocket serverSocket = null;
Socket clientSocket = null;
try
{
serverSocket = new ServerSocket(nPort);
serverOut.writeBytes(sr_port);
clientSocket = serverSocket.accept();
}
catch(IOException e)
{
System.out.println(e);
}
}
}
}
Client code:
class client {
public static void main(String argv[]) throws Exception
{
String serverIp = argv[0];
String msg = argv[2];
int port = Integer.parseInt(argv[1]);
Socket clientSocket = new Socket(InetAddress.getByName(serverIp), port);
BufferedReader clientIn =
new BufferedReader(new
InputStreamReader(clientSocket.getInputStream()));
String inMsg_rport = clientIn.readLine();
System.out.println("FROM SERVER: " + inMsg_rport);
int r_port = Integer.parseInt(inMsg_rport);
clientSocket.close();
System.out.println("Closed connection");
Socket new_clientSocket = new Socket(InetAddress.getByName(serverIp), r_port);
}
}
readLine() in your client is a blocking call, waiting for an end-of-line character
http://docs.oracle.com/javase/6/docs/api/java/io/BufferedReader.html#readLine()
You aren't sending an end of line character. You're using a DataOutputStream in your server and sending raw bytes.
Don't use a DataOutputStream in your server; I don't think that's really what you're looking for. Just send the port number as text with an end of line character and be done with it.