Develop Reference

Running a live Java Server on Amazon AWS

I am developing a Client-Server application with several other programmers, in Java. At this point in time I do not want to be running the code locally. I want to be able to connect to the Server from any machine.
I wrote a test server and test client, just to make sure that things are working properly. But they are not. I am using Amazon AWS EC2 Linux that comes with Java. I am able to compile and run my Server after I SSH into the EC2, but the Client on my local disk is just not connecting. Here is the code.
// Code found online (https://cs.lmu.edu/~ray/notes/javanetexamples/)
import java.io.IOException;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;
import java.util.concurrent.Executors;
import java.util.concurrent.ExecutorService;
public class TestServer {
public static void main(String[] args) throws Exception {
try (ServerSocket listener = new ServerSocket(50000)) {
System.out.println("The capitalization server is running...");
System.out.println(listener.getInetAddress());
ExecutorService pool = Executors.newFixedThreadPool(20);
while (true) {
pool.execute(new Capitalizer(listener.accept()));
}
}
}
private static class Capitalizer implements Runnable {
private Socket socket;
Capitalizer(Socket socket) {
this.socket = socket;
}
#Override
public void run() {
System.out.println("Connected: " + socket);
try {
Scanner in = new Scanner(socket.getInputStream());
PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
while (in.hasNextLine()) {
out.println(in.nextLine().toUpperCase());
}
} catch (Exception e) {
System.out.println("Error:" + socket);
} finally {
try { socket.close(); } catch (IOException e) {}
System.out.println("Closed: " + socket);
}
}
}
}
// Code found online (https://cs.lmu.edu/~ray/notes/javanetexamples/)
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.Scanner;
public class TestClient {
public static void main(String[] args) throws Exception {
try (Socket socket = new Socket("ADDRESS HERE", 50000)) {
System.out.println("Enter lines of text then Ctrl+D or Ctrl+C to quit");
Scanner scanner = new Scanner(System.in);
Scanner in = new Scanner(socket.getInputStream());
PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
while (scanner.hasNextLine()) {
out.println(scanner.nextLine());
System.out.println(in.nextLine());
}
}
}
}
In place of "ADDRESS HERE" in the Client, I have tried the private IP and public IP of my Amazon EC2 instance. I have also tried the public DNS name. Nothing seems to work. There is just no connection from the Client to the Server. In fact, "Enter lines of text then Ctrl+D or Ctrl+C to quit" never prints.
All help is appreciated. Thank you.

Allow your IP address to send request to the EC2. For this, you need to go to your Security Group and add your IP there. Follow these steps-
GO to your AWS console.
Click on EC2, then under Resources you will find Security Groups.
Select your security group.
Follow the steps in the given image.

Since you're able to connect to EC2 instance via SSH, your Security Group allows this.
Now you need to allow requests from the client in this Security Group. You will either need to provide a concrete IP, IP range or allow all IPs (not recommended) in the group.
You can find how to do this here.

HttpServer with more than one responder

In my application (java) I need to support two types of RPCs:
Administration RPC and User RPC. I am using avro to create these RPCs, currently I am opening two HttpServers one per RPC using code similar to the following:
Server serverAdmins = new HttpServer(new ReflectResponder(AdministrationRPC.class, arpcImpl), adminRpcPort);
Server serverUsers = new HttpServer(new ReflectResponder(UsersRPC.class, urpcImpl), usersRpcPort);
...
This works, but it look like a waste for me - I am looking for a way to use a single http server with two ports or two urls on the same port (any of these options is good for me), something like:
Server server = new new HttpServer(new ReflectResponder(AdministrationRPC.class, arpcImpl), adminRpcPort);
server.addResponder(new ReflectResponder(UsersRPC.class, urpcImpl), usersRpcPort);
...
the addResponder method does not exists of course, the only method that looks similar is the addConnector method - but even after thorough googling I couldn't find how to apply it to my needs..
Is there a way to start two avro responders on the same http server?

I managed to resolve this issue by writing a simple class which allow for what I want, see code below.
import java.io.IOException;
import java.net.URL;
import org.apache.avro.ipc.HttpTransceiver;
import org.apache.avro.ipc.Responder;
import org.apache.avro.ipc.ResponderServlet;
import org.apache.avro.ipc.reflect.ReflectRequestor;
import org.apache.avro.ipc.reflect.ReflectResponder;
import org.mortbay.jetty.Server;
import org.mortbay.jetty.servlet.Context;
import org.mortbay.jetty.servlet.ServletHolder;
/**
*
* #author bennyl
*/
public class MultiResponderHttpServer {
private final Context context;
private final Server server;
private final int port;
public MultiResponderHttpServer(int port) {
this.port = port;
server = new Server(port);
context = new Context(server, "/", Context.SESSIONS);
}
public void addResponder(String baseUri, Responder responder) throws IOException {
ResponderServlet servlet = new ResponderServlet(responder);
ServletHolder holder = new ServletHolder(servlet);
context.addServlet(holder, baseUri);
}
public int getPort() {
return port;
}
public void close() throws Exception {
server.stop();
}
public void start() throws Exception {
server.start();
}
public void join() throws InterruptedException {
server.join();
}
public static void main(String[] args) throws IOException, InterruptedException {
MultiResponderHttpServer server = new MultiResponderHttpServer(8888);
server.addResponder("/test_a/*", new ReflectResponder(TestProtocol.class,
(TestProtocol) why -> "a received a message: '" + why + "'"));
server.addResponder("/test_b/*", new ReflectResponder(TestProtocol.class,
(TestProtocol) why -> "b received a message: '" + why + "'"));
server.start();
HttpTransceiver atrans = new HttpTransceiver(new URL("http://localhost:" + server.getPort() + "/test_a/"));
HttpTransceiver btrans = new HttpTransceiver(new URL("http://localhost:" + server.getPort() + "/test_b/"));
System.out.println(ReflectRequestor.getClient(TestProtocol.class, atrans).go("message to a"));
System.out.println(ReflectRequestor.getClient(TestProtocol.class, btrans).go("message to b"));
server.close();
server.join();
}
public interface TestProtocol {
String go(String why);
}
}

How can I test a simple Server -- Client Application on my own machine at home?

I want to test this simpel server-client application on my own machine at home. How can I run this in Eclipse and then see if the other side can see my message. I want to at some point be able to make a chat window that anyone could have on their machine and send messages to anyone that is online that is linked into the chat window.
But first I have to be able to see that I have a connection. Should I install a server on my computer, or someone told me that there was a server already installed on my computer but I just had to have windows turn it on. (Windows 7)
Question: How can I test this client-server on my computer at home?
Code:
Client Side:
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);
}
}
Server side:
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();
}
}
}
Code I want to Add for new message:
out.println("Hello Doug, how are you!);
This will not show in my message box when it shows up on the screen. Is 127.0.0.1 always the IP address that needs to be entered when testing from eclipse or how would I change this around so that I could let the user determine their own IP address.

You can just open two terminals. For the DateClient, just use localhost or 127.0.0.1 as the address. If you really must use Eclipse, then you can run one of the program from Eclipse and the other from a terminal.

You don't need any server.
In Eclipse (assuming your coding is correct), you can run multiple programs (Java files with a main method) simultaneously.
First, say DateServer -> Run As -> Java Application
Next, say DateClient -> Run As -> Java Application
To run this, you don't need any additional server, but Win 7 might ask you for permissions to unblock these programs from accessing the network. You should say yes to these permissions.
If you want to get a feel of separate client and server, this might be better
Keep the DateClient and DateServer in two different projects
Compile both projects as JARs
Open two different DOS consoles and run these two applications in these separate DOS consoles.

Client Side :
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;
import java.util.logging.Level;
import java.util.logging.Logger;
public class ClientSide {
public static void main(String[] args) {
try {
Socket s = new Socket("localhost", 1234);
DataOutputStream dos = new DataOutputStream(s.getOutputStream());
dos.writeUTF("Hello");
} catch (IOException ex) {
System.out.println("Connection failed");
}
}
}
Server Side :
import java.io.DataInputStream;
import java.io.IOException;
import java.net.ServerSocket;
public class ServerSide {
public static void main(String[] args) {
try {
ServerSocket ss = new ServerSocket(1234);
System.out.println("waiting for connection...");
DataInputStream dis = new DataInputStream(ss.accept().getInputStream());
System.out.println("Successfully Connected\n" + dis.readUTF());
} catch (IOException ex) {
System.out.println("Server Not Started : " + ex);
}
}
}

Java Socket Server for Game Login/Authentication

I am currently working on a Java Application using the classes under java.net.* for a MMORPG I am creating. It'll be connected with a Unity3D Game (using .NET Sockets for TCP). I am unsure how to handle the login/authentication of players.
Suggestions? I was thinking about handling authentication this via a secure form over https, creating and storing a temporary login key in the database, and then sending the key back to the client, allotting them a minute to connect to a game server using the randomly generated key. Is this a secure and reliable solution, or is there something better I can do?
Server Class
import java.io.IOException;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
public class Server extends Thread {
public static final int MAX_CLIENTS = 500;
private ServerSocket listener;
protected ArrayList<Client> clients;
public Server(int listenPort) throws IOException {
listener = new ServerSocket(
listenPort, MAX_CLIENTS,
InetAddress.getLocalHost()
);
clients = new ArrayList<Client>();
}
#Override
public void run() {
while (true) {
try {
Socket socket = listener.accept();
Client client = new Client(socket, this);
clients.add(client);
new Thread(client).start();
} catch (IOException e) {}
}
}
public static void main(String[] args) throws IOException {
new Server(4428).start();
}
}
Client Class
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
public class Client implements Runnable {
private Socket socket;
private Server server;
private BufferedReader in;
private PrintWriter out;
public Client(Socket sock, Server serv) {
socket = sock;
server = serv;
in = null;
out = null;
}
#Override
public void run() {
try {
in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
out = new PrintWriter(socket.getOutputStream(), true);
while (true) {
// Read Data with read()
}
} catch (IOException e) {}
}
public void read() throws IOException {
}
public void send(String data) {
}
}

I would recommend using HTTPS for login and for important account actions (buy/sell/transfer items). When the client logins to the server over HTTPS the server should generate a long (64-128 bytes) random session id that is stored in the database. Also generate a temporary one-time authentication token (long random value) for the client's TCP connection.
The reason for using HTTPS is to help stop MITM attacks from stealing the users in game assets.
If the traffic between client & server is low you could use a TLS socket instead of a normal TCP socket. Just make sure to have the client validate(Signed by a trusted CA and that the domain matches) the server's certificate.
Even if you use HTTPS for important actions a MITM attack could still mess with the users actions (moving, attacking, chat) or change what the user sees (hide monsters or other users).

Simple HTTP server in Java using only Java SE API

Is there a way to create a very basic HTTP server (supporting only GET/POST) in Java using just the Java SE API, without writing code to manually parse HTTP requests and manually format HTTP responses? The Java SE API nicely encapsulates the HTTP client functionality in HttpURLConnection, but is there an analog for HTTP server functionality?
Just to be clear, the problem I have with a lot of ServerSocket examples I've seen online is that they do their own request parsing/response formatting and error handling, which is tedious, error-prone, and not likely to be comprehensive, and I'm trying to avoid it for those reasons.

Since Java SE 6, there's a builtin HTTP server in Sun Oracle JRE. The Java 9 module name is jdk.httpserver. The com.sun.net.httpserver package summary outlines the involved classes and contains examples.
Here's a kickoff example copypasted from their docs. You can just copy'n'paste'n'run it on Java 6+.
(to all people trying to edit it nonetheless, because it's an ugly piece of code, please don't, this is a copy paste, not mine, moreover you should never edit quotations unless they have changed in the original source)
package com.stackoverflow.q3732109;
import java.io.IOException;
import java.io.OutputStream;
import java.net.InetSocketAddress;
import com.sun.net.httpserver.HttpExchange;
import com.sun.net.httpserver.HttpHandler;
import com.sun.net.httpserver.HttpServer;
public class Test {
public static void main(String[] args) throws Exception {
HttpServer server = HttpServer.create(new InetSocketAddress(8000), 0);
server.createContext("/test", new MyHandler());
server.setExecutor(null); // creates a default executor
server.start();
}
static class MyHandler implements HttpHandler {
#Override
public void handle(HttpExchange t) throws IOException {
String response = "This is the response";
t.sendResponseHeaders(200, response.length());
OutputStream os = t.getResponseBody();
os.write(response.getBytes());
os.close();
}
}
}
Noted should be that the response.length() part in their example is bad, it should have been response.getBytes().length. Even then, the getBytes() method must explicitly specify the charset which you then specify in the response header. Alas, albeit misguiding to starters, it's after all just a basic kickoff example.
Execute it and go to http://localhost:8000/test and you'll see the following response:
This is the response
As to using com.sun.* classes, do note that this is, in contrary to what some developers think, absolutely not forbidden by the well known FAQ Why Developers Should Not Write Programs That Call 'sun' Packages. That FAQ concerns the sun.* package (such as sun.misc.BASE64Encoder) for internal usage by the Oracle JRE (which would thus kill your application when you run it on a different JRE), not the com.sun.* package. Sun/Oracle also just develop software on top of the Java SE API themselves like as every other company such as Apache and so on. Moreover, this specific HttpServer must be present in every JDK so there is absolutely no means of "portability" issue like as would happen with sun.* package. Using com.sun.* classes is only discouraged (but not forbidden) when it concerns an implementation of a certain Java API, such as GlassFish (Java EE impl), Mojarra (JSF impl), Jersey (JAX-RS impl), etc.

Check out NanoHttpd
NanoHTTPD is a light-weight HTTP server designed for embedding in other applications, released under a Modified BSD licence.
It is being developed at Github and uses Apache Maven for builds & unit testing"

The com.sun.net.httpserver solution is not portable across JREs. Its better to use the official webservices API in javax.xml.ws to bootstrap a minimal HTTP server...
import java.io._
import javax.xml.ws._
import javax.xml.ws.http._
import javax.xml.transform._
import javax.xml.transform.stream._
#WebServiceProvider
#ServiceMode(value=Service.Mode.PAYLOAD)
class P extends Provider[Source] {
def invoke(source: Source) = new StreamSource( new StringReader("<p>Hello There!</p>"));
}
val address = "http://127.0.0.1:8080/"
Endpoint.create(HTTPBinding.HTTP_BINDING, new P()).publish(address)
println("Service running at "+address)
println("Type [CTRL]+[C] to quit!")
Thread.sleep(Long.MaxValue)
EDIT: this actually works! The above code looks like Groovy or something. Here is a translation to Java which I tested:
import java.io.*;
import javax.xml.ws.*;
import javax.xml.ws.http.*;
import javax.xml.transform.*;
import javax.xml.transform.stream.*;
#WebServiceProvider
#ServiceMode(value = Service.Mode.PAYLOAD)
public class Server implements Provider<Source> {
public Source invoke(Source request) {
return new StreamSource(new StringReader("<p>Hello There!</p>"));
}
public static void main(String[] args) throws InterruptedException {
String address = "http://127.0.0.1:8080/";
Endpoint.create(HTTPBinding.HTTP_BINDING, new Server()).publish(address);
System.out.println("Service running at " + address);
System.out.println("Type [CTRL]+[C] to quit!");
Thread.sleep(Long.MAX_VALUE);
}
}

I like this question because this is an area where there's continuous innovation and there's always a need to have a light server especially when talking about embedded servers in small(er) devices. I think answers fall into two broad groups.
Thin-server: server-up static content with minimal processing, context or session processing.
Small-server: ostensibly a has many httpD-like server qualities with as small a footprint as you can get away with.
While I might consider HTTP libraries like: Jetty, Apache Http Components, Netty and others to be more like a raw HTTP processing facilities. The labelling is very subjective, and depends on the kinds of thing you've been call-on to deliver for small-sites. I make this distinction in the spirit of the question, particularly the remark about...
"...without writing code to manually parse HTTP requests and manually format HTTP responses..."
These raw tools let you do that (as described in other answers). They don't really lend themselves to a ready-set-go style of making a light, embedded or mini-server. A mini-server is something that can give you similar functionality to a full-function web server (like say, Tomcat) without bells and whistles, low volume, good performance 99% of the time. A thin-server seems closer to the original phrasing just a bit more than raw perhaps with a limited subset functionality, enough to make you look good 90% of the time. My idea of raw would be makes me look good 75% - 89% of the time without extra design and coding. I think if/when you reach the level of WAR files, we've left the "small" for bonsi servers that looks like everything a big server does smaller.
Thin-server options
Grizzly
UniRest (multiple-languages)
NanoHTTPD (just one file)
Mini-server options:
Spark Java ... Good things are possible with lots of helper constructs like Filters, Templates, etc.
MadVoc ... aims to be bonsai and could well be such ;-)
Among the other things to consider, I'd include authentication, validation, internationalisation, using something like FreeMaker or other template tool to render page output. Otherwise managing HTML editing and parameterisation is likely to make working with HTTP look like noughts-n-crosses. Naturally it all depends on how flexible you need to be. If it's a menu-driven FAX machine it can be very simple. The more interactions, the 'thicker' your framework needs to be. Good question, good luck!

Have a look at the "Jetty" web server Jetty. Superb piece of Open Source software that would seem to meet all your requirments.
If you insist on rolling your own then have a look at the "httpMessage" class.

Once upon a time I was looking for something similar - a lightweight yet fully functional HTTP server that I could easily embed and customize. I found two types of potential solutions:
Full servers that are not all that lightweight or simple (for an extreme definition of lightweight.)
Truly lightweight servers that aren't quite HTTP servers, but glorified ServerSocket examples that are not even remotely RFC-compliant and don't support commonly needed basic functionality.
So... I set out to write JLHTTP - The Java Lightweight HTTP Server.
You can embed it in any project as a single (if rather long) source file, or as a ~50K jar (~35K stripped) with no dependencies. It strives to be RFC-compliant and includes extensive documentation and many useful features while keeping bloat to a minimum.
Features include: virtual hosts, file serving from disk, mime type mappings via standard mime.types file, directory index generation, welcome files, support for all HTTP methods, conditional ETags and If-* header support, chunked transfer encoding, gzip/deflate compression, basic HTTPS (as provided by the JVM), partial content (download continuation), multipart/form-data handling for file uploads, multiple context handlers via API or annotations, parameter parsing (query string or x-www-form-urlencoded body), etc.
I hope others find it useful :-)

Spark is the simplest, here is a quick start guide: http://sparkjava.com/

All the above answers details about Single main threaded Request Handler.
setting:
server.setExecutor(java.util.concurrent.Executors.newCachedThreadPool());
Allows multiple request serving via multiple threads using executor service.
So the end code will be something like below:
import java.io.IOException;
import java.io.OutputStream;
import java.net.InetSocketAddress;
import com.sun.net.httpserver.HttpExchange;
import com.sun.net.httpserver.HttpHandler;
import com.sun.net.httpserver.HttpServer;
public class App {
public static void main(String[] args) throws Exception {
HttpServer server = HttpServer.create(new InetSocketAddress(8000), 0);
server.createContext("/test", new MyHandler());
//Thread control is given to executor service.
server.setExecutor(java.util.concurrent.Executors.newCachedThreadPool());
server.start();
}
static class MyHandler implements HttpHandler {
#Override
public void handle(HttpExchange t) throws IOException {
String response = "This is the response";
long threadId = Thread.currentThread().getId();
System.out.println("I am thread " + threadId );
response = response + "Thread Id = "+threadId;
t.sendResponseHeaders(200, response.length());
OutputStream os = t.getResponseBody();
os.write(response.getBytes());
os.close();
}
}
}

It's possible to create an httpserver that provides basic support for J2EE servlets with just the JDK and the servlet api in a just a few lines of code.
I've found this very useful for unit testing servlets, as it starts much faster than other lightweight containers (we use jetty for production).
Most very lightweight httpservers do not provide support for servlets, but we need them, so I thought I'd share.
The below example provides basic servlet support, or throws and UnsupportedOperationException for stuff not yet implemented. It uses the com.sun.net.httpserver.HttpServer for basic http support.
import java.io.*;
import java.lang.reflect.*;
import java.net.InetSocketAddress;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
import com.sun.net.httpserver.HttpExchange;
import com.sun.net.httpserver.HttpHandler;
import com.sun.net.httpserver.HttpServer;
#SuppressWarnings("deprecation")
public class VerySimpleServletHttpServer {
HttpServer server;
private String contextPath;
private HttpHandler httpHandler;
public VerySimpleServletHttpServer(String contextPath, HttpServlet servlet) {
this.contextPath = contextPath;
httpHandler = new HttpHandlerWithServletSupport(servlet);
}
public void start(int port) throws IOException {
InetSocketAddress inetSocketAddress = new InetSocketAddress(port);
server = HttpServer.create(inetSocketAddress, 0);
server.createContext(contextPath, httpHandler);
server.setExecutor(null);
server.start();
}
public void stop(int secondsDelay) {
server.stop(secondsDelay);
}
public int getServerPort() {
return server.getAddress().getPort();
}
}
final class HttpHandlerWithServletSupport implements HttpHandler {
private HttpServlet servlet;
private final class RequestWrapper extends HttpServletRequestWrapper {
private final HttpExchange ex;
private final Map<String, String[]> postData;
private final ServletInputStream is;
private final Map<String, Object> attributes = new HashMap<>();
private RequestWrapper(HttpServletRequest request, HttpExchange ex, Map<String, String[]> postData, ServletInputStream is) {
super(request);
this.ex = ex;
this.postData = postData;
this.is = is;
}
#Override
public String getHeader(String name) {
return ex.getRequestHeaders().getFirst(name);
}
#Override
public Enumeration<String> getHeaders(String name) {
return new Vector<String>(ex.getRequestHeaders().get(name)).elements();
}
#Override
public Enumeration<String> getHeaderNames() {
return new Vector<String>(ex.getRequestHeaders().keySet()).elements();
}
#Override
public Object getAttribute(String name) {
return attributes.get(name);
}
#Override
public void setAttribute(String name, Object o) {
this.attributes.put(name, o);
}
#Override
public Enumeration<String> getAttributeNames() {
return new Vector<String>(attributes.keySet()).elements();
}
#Override
public String getMethod() {
return ex.getRequestMethod();
}
#Override
public ServletInputStream getInputStream() throws IOException {
return is;
}
#Override
public BufferedReader getReader() throws IOException {
return new BufferedReader(new InputStreamReader(getInputStream()));
}
#Override
public String getPathInfo() {
return ex.getRequestURI().getPath();
}
#Override
public String getParameter(String name) {
String[] arr = postData.get(name);
return arr != null ? (arr.length > 1 ? Arrays.toString(arr) : arr[0]) : null;
}
#Override
public Map<String, String[]> getParameterMap() {
return postData;
}
#Override
public Enumeration<String> getParameterNames() {
return new Vector<String>(postData.keySet()).elements();
}
}
private final class ResponseWrapper extends HttpServletResponseWrapper {
final ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
final ServletOutputStream servletOutputStream = new ServletOutputStream() {
#Override
public void write(int b) throws IOException {
outputStream.write(b);
}
};
private final HttpExchange ex;
private final PrintWriter printWriter;
private int status = HttpServletResponse.SC_OK;
private ResponseWrapper(HttpServletResponse response, HttpExchange ex) {
super(response);
this.ex = ex;
printWriter = new PrintWriter(servletOutputStream);
}
#Override
public void setContentType(String type) {
ex.getResponseHeaders().add("Content-Type", type);
}
#Override
public void setHeader(String name, String value) {
ex.getResponseHeaders().add(name, value);
}
#Override
public javax.servlet.ServletOutputStream getOutputStream() throws IOException {
return servletOutputStream;
}
#Override
public void setContentLength(int len) {
ex.getResponseHeaders().add("Content-Length", len + "");
}
#Override
public void setStatus(int status) {
this.status = status;
}
#Override
public void sendError(int sc, String msg) throws IOException {
this.status = sc;
if (msg != null) {
printWriter.write(msg);
}
}
#Override
public void sendError(int sc) throws IOException {
sendError(sc, null);
}
#Override
public PrintWriter getWriter() throws IOException {
return printWriter;
}
public void complete() throws IOException {
try {
printWriter.flush();
ex.sendResponseHeaders(status, outputStream.size());
if (outputStream.size() > 0) {
ex.getResponseBody().write(outputStream.toByteArray());
}
ex.getResponseBody().flush();
} catch (Exception e) {
e.printStackTrace();
} finally {
ex.close();
}
}
}
public HttpHandlerWithServletSupport(HttpServlet servlet) {
this.servlet = servlet;
}
#SuppressWarnings("deprecation")
#Override
public void handle(final HttpExchange ex) throws IOException {
byte[] inBytes = getBytes(ex.getRequestBody());
ex.getRequestBody().close();
final ByteArrayInputStream newInput = new ByteArrayInputStream(inBytes);
final ServletInputStream is = new ServletInputStream() {
#Override
public int read() throws IOException {
return newInput.read();
}
};
Map<String, String[]> parsePostData = new HashMap<>();
try {
parsePostData.putAll(HttpUtils.parseQueryString(ex.getRequestURI().getQuery()));
// check if any postdata to parse
parsePostData.putAll(HttpUtils.parsePostData(inBytes.length, is));
} catch (IllegalArgumentException e) {
// no postData - just reset inputstream
newInput.reset();
}
final Map<String, String[]> postData = parsePostData;
RequestWrapper req = new RequestWrapper(createUnimplementAdapter(HttpServletRequest.class), ex, postData, is);
ResponseWrapper resp = new ResponseWrapper(createUnimplementAdapter(HttpServletResponse.class), ex);
try {
servlet.service(req, resp);
resp.complete();
} catch (ServletException e) {
throw new IOException(e);
}
}
private static byte[] getBytes(InputStream in) throws IOException {
ByteArrayOutputStream out = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
while (true) {
int r = in.read(buffer);
if (r == -1)
break;
out.write(buffer, 0, r);
}
return out.toByteArray();
}
#SuppressWarnings("unchecked")
private static <T> T createUnimplementAdapter(Class<T> httpServletApi) {
class UnimplementedHandler implements InvocationHandler {
#Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
throw new UnsupportedOperationException("Not implemented: " + method + ", args=" + Arrays.toString(args));
}
}
return (T) Proxy.newProxyInstance(UnimplementedHandler.class.getClassLoader(),
new Class<?>[] { httpServletApi },
new UnimplementedHandler());
}
}

You may also have a look at some NIO application framework such as:
Netty: http://jboss.org/netty
Apache Mina: http://mina.apache.org/ or its subproject AsyncWeb: http://mina.apache.org/asyncweb/

This code is better than ours, you only need to add 2 libs: javax.servelet.jar and org.mortbay.jetty.jar.
Class Jetty:
package jetty;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.mortbay.http.SocketListener;
import org.mortbay.jetty.Server;
import org.mortbay.jetty.servlet.ServletHttpContext;
public class Jetty {
public static void main(String[] args) {
try {
Server server = new Server();
SocketListener listener = new SocketListener();
System.out.println("Max Thread :" + listener.getMaxThreads() + " Min Thread :" + listener.getMinThreads());
listener.setHost("localhost");
listener.setPort(8070);
listener.setMinThreads(5);
listener.setMaxThreads(250);
server.addListener(listener);
ServletHttpContext context = (ServletHttpContext) server.getContext("/");
context.addServlet("/MO", "jetty.HelloWorldServlet");
server.start();
server.join();
/*//We will create our server running at http://localhost:8070
Server server = new Server();
server.addListener(":8070");
//We will deploy our servlet to the server at the path '/'
//it will be available at http://localhost:8070
ServletHttpContext context = (ServletHttpContext) server.getContext("/");
context.addServlet("/MO", "jetty.HelloWorldServlet");
server.start();
*/
} catch (Exception ex) {
Logger.getLogger(Jetty.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
Servlet class:
package jetty;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class HelloWorldServlet extends HttpServlet
{
#Override
protected void doGet(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) throws ServletException, IOException
{
String appid = httpServletRequest.getParameter("appid");
String conta = httpServletRequest.getParameter("conta");
System.out.println("Appid : "+appid);
System.out.println("Conta : "+conta);
httpServletResponse.setContentType("text/plain");
PrintWriter out = httpServletResponse.getWriter();
out.println("Hello World!");
out.close();
}
}

I can strongly recommend looking into Simple, especially if you don't need Servlet capabilities but simply access to the request/reponse objects. If you need REST you can put Jersey on top of it, if you need to output HTML or similar there's Freemarker. I really love what you can do with this combination, and there is relatively little API to learn.

Starting in Java 18, you can create simple web servers with Java standard library:
class Main {
public static void main(String[] args) {
var port = 8000;
var rootDirectory = Path.of("C:/Users/Mahozad/Desktop/");
var outputLevel = OutputLevel.VERBOSE;
var server = SimpleFileServer.createFileServer(
new InetSocketAddress(port),
rootDirectory,
outputLevel
);
server.start();
}
}
This will, by default, show a directory listing of the root directory you specified. You can place an index.html file (and other assets like CSS and JS files) in that directory to show them instead.
Example (I put these in Desktop which was specified as my directory root above):
index.html:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Java 18 Simple Web Server</title>
<link rel="stylesheet" href="styles.css">
<style>h1 { color: blue; }</style>
<script src="scripts.js" defer>
let element = document.getElementsByTagName("h1")[0];
element.style.fontSize = "48px";
</script>
</head>
<body>
<h1>I'm <i>index.html</i> in the root directory.</h1>
</body>
</html>
Sidenote
For Java standard library HTTP client, see the post Java 11 new HTTP Client API.

An example of a very basic HTTP server on TCP sockets level:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
public class NaiveHttpServer {
public static void main(String[] args) throws IOException {
String hostname = InetAddress.getLocalHost().getHostName();
ServerSocket serverSocket = new ServerSocket(8089);
while (true) {
Socket clientSocket = serverSocket.accept();
PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
String s = in.readLine();
System.out.println(s);
while ("\r\n".equals(in.readLine()));
if ("GET /hostname HTTP/1.1".equals(s)) {
out.println("HTTP/1.1 200 OK");
out.println("Connection: close");
out.println("Content-Type: text/plain");
out.println("Content-Length:" + hostname.length());
out.println();
out.println(hostname);
} else {
out.println("HTTP/1.1 404 Not Found");
out.println("Connection: close");
out.println();
}
out.flush();
}
}
}
The example serves the hostname of the computer.

checkout Simple. its a pretty simple embeddable server with built in support for quite a variety of operations. I particularly love its threading model..
Amazing!

Check out takes. Look at https://github.com/yegor256/takes for quick info

Try this https://github.com/devashish234073/Java-Socket-Http-Server/blob/master/README.md
This API has creates an HTTP server using sockets.
It gets a request from the browser as text
Parses it to retrieve URL info, method, attributes, etc.
Creates dynamic response using the URL mapping defined
Sends the response to the browser.
For example the here's how the constructor in the Response.java class converts a raw response into an http response:
public Response(String resp){
Date date = new Date();
String start = "HTTP/1.1 200 OK\r\n";
String header = "Date: "+date.toString()+"\r\n";
header+= "Content-Type: text/html\r\n";
header+= "Content-length: "+resp.length()+"\r\n";
header+="\r\n";
this.resp=start+header+resp;
}

How about Apache Commons HttpCore project?
From the web site:...
HttpCore Goals
Implementation of the most fundamental HTTP transport aspects
Balance between good performance and the clarity & expressiveness of
API
Small (predictable) memory footprint
Self contained library (no external dependencies beyond JRE)

You can write a pretty simple embedded Jetty Java server.
Embedded Jetty means that the server (Jetty) shipped together with the application as opposed of deploying the application on external Jetty server.
So if in non-embedded approach your webapp built into WAR file which deployed to some external server (Tomcat / Jetty / etc), in embedded Jetty, you write the webapp and instantiate the jetty server in the same code base.
An example for embedded Jetty Java server you can git clone and use: https://github.com/stas-slu/embedded-jetty-java-server-example

The old com.sun.net.httpserver is again a public and accepted API, since Java 11. You can get it as HttpServer class, available as part of jdk.httpserver module. See https://docs.oracle.com/en/java/javase/11/docs/api/jdk.httpserver/com/sun/net/httpserver/HttpServer.html
This class implements a simple HTTP server. A HttpServer is bound to an IP address and port number and listens for incoming TCP connections from clients on this address. The sub-class HttpsServer implements a server which handles HTTPS requests.
So, apart from its limitations, there is no reason to avoid its use anymore.
I use it to publish a control interface in server applications. Reading the User-agent header from a client request I even respond in text/plain to CLI tools like curl or in more elegant HTML way to any other browser.
Cool and easy.

Here is my simple webserver, used in JMeter for testing webhooks (that's why it will close and end itself after request is received).
import java.io.IOException;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
public class HttpServer {
private static int extractContentLength(StringBuilder sb) {
int length = 0;
String[] lines = sb.toString().split("\\n");
for (int i = 0; i < lines.length; i++) {
String s = lines[i];
if (s.toLowerCase().startsWith("Content-Length:".toLowerCase()) && i <= lines.length - 2) {
String slength = s.substring(s.indexOf(":") + 1, s.length()).trim();
length = Integer.parseInt(slength);
System.out.println("Length = " + length);
return length;
}
}
return 0;
}
public static void main(String[] args) throws IOException {
int port = Integer.parseInt(args[0]);
System.out.println("starting HTTP Server on port " + port);
StringBuilder outputString = new StringBuilder(1000);
ServerSocket serverSocket = new ServerSocket(port);
serverSocket.setSoTimeout(3 * 60 * 1000); // 3 minutes timeout
while (true) {
outputString.setLength(0); // reset buff
Socket clientSocket = serverSocket.accept(); // blocking
PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
try {
boolean isBodyRead = false;
int dataBuffer;
while ((dataBuffer = clientSocket.getInputStream().read()) != -1) {
if (dataBuffer == 13) { // CR
if (clientSocket.getInputStream().read() == 10) { // LF
outputString.append("\n");
}
} else {
outputString.append((char) dataBuffer);
}
// do we have Content length
int len = extractContentLength(outputString);
if (len > 0) {
int actualLength = len - 1; // we need to substract \r\n
for (int i = 0; i < actualLength; i++) {
int body = clientSocket.getInputStream().read();
outputString.append((char) body);
}
isBodyRead = true;
break;
}
} // end of reading while
if (isBodyRead) {
// response headers
out.println("HTTP/1.1 200 OK");
out.println("Connection: close");
out.println(); // must have empty line for HTTP
out.flush();
out.close(); // close clients connection
}
} catch (IOException ioEx) {
System.out.println(ioEx.getMessage());
}
System.out.println(outputString.toString());
break; // stop server - break while true
} // end of outer while true
serverSocket.close();
} // end of method
}
You can test it like this:
curl -X POST -H "Content-Type: application/json" -H "Connection: close" -d '{"name": "gustinmi", "email": "gustinmi at google dot com "}' -v http://localhost:8081/

I had some fun, I toyed around and pieced together this. I hope it helps you.
You are going to need Gradle installed or use Maven with a plugin.
build.gradle
plugins {
id 'application'
}
group 'foo.bar'
version '1.0'
repositories {
mavenCentral()
}
application{
mainClass.set("foo.FooServer")
}
dependencies {}
FooServer
The main entry point, your main class.
package foo;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.nio.ByteBuffer;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class FooServer {
public static void main(String[] args) throws IOException {
ServerSocket serverSocket = new ServerSocket(7654);
serverSocket.setPerformancePreferences(0, 1, 2);
/* the higher the numbers, the better the concurrent performance, ha!
we found that a 3:7 ratio to be optimal
3 partitioned executors to 7 network executors */
ExecutorService executors = Executors.newFixedThreadPool(3);
executors.execute(new PartitionedExecutor(serverSocket));
}
public static class PartitionedExecutor implements Runnable {
ServerSocket serverSocket;
public PartitionedExecutor(ServerSocket serverSocket) {
this.serverSocket = serverSocket;
}
#Override
public void run() {
ExecutorService executors = Executors.newFixedThreadPool(30);
executors.execute(new NetworkRequestExecutor(serverSocket, executors));
}
}
public static class NetworkRequestExecutor implements Runnable{
String IGNORE_CHROME = "/favicon.ico";
String BREAK = "\r\n";
String DOUBLEBREAK = "\r\n\r\n";
Integer REQUEST_METHOD = 0;
Integer REQUEST_PATH = 1;
Integer REQUEST_VERSION = 2;
String RENDERER;
Socket socketClient;
ExecutorService executors;
ServerSocket serverSocket;
public NetworkRequestExecutor(ServerSocket serverSocket, ExecutorService executors){
this.serverSocket = serverSocket;
this.executors = executors;
}
#Override
public void run() {
try {
socketClient = serverSocket.accept();
Thread.sleep(19);//do this for safari, its a hack but safari requires something like this.
InputStream requestInputStream = socketClient.getInputStream();
OutputStream clientOutput = socketClient.getOutputStream();
if (requestInputStream.available() == 0) {
requestInputStream.close();
clientOutput.flush();
clientOutput.close();
executors.execute(new NetworkRequestExecutor(serverSocket, executors));
return;
}
ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
int bytesRead;
while ((bytesRead = requestInputStream.read(byteBuffer.array())) != -1) {
byteArrayOutputStream.write(byteBuffer.array(), 0, bytesRead);
if (requestInputStream.available() == 0) break;
}
String completeRequestContent = byteArrayOutputStream.toString();
String[] requestBlocks = completeRequestContent.split(DOUBLEBREAK, 2);
String headerComponent = requestBlocks[0];
String[] methodPathComponentsLookup = headerComponent.split(BREAK);
String methodPathComponent = methodPathComponentsLookup[0];
String[] methodPathVersionComponents = methodPathComponent.split("\\s");
String requestVerb = methodPathVersionComponents[REQUEST_METHOD];
String requestPath = methodPathVersionComponents[REQUEST_PATH];
String requestVersion = methodPathVersionComponents[REQUEST_VERSION];
if (requestPath.equals(IGNORE_CHROME)) {
requestInputStream.close();
clientOutput.flush();
clientOutput.close();
executors.execute(new NetworkRequestExecutor(serverSocket, executors));
return;
}
ConcurrentMap<String, String> headers = new ConcurrentHashMap<>();
String[] headerComponents = headerComponent.split(BREAK);
for (String headerLine : headerComponents) {
String[] headerLineComponents = headerLine.split(":");
if (headerLineComponents.length == 2) {
String fieldKey = headerLineComponents[0].trim();
String content = headerLineComponents[1].trim();
headers.put(fieldKey.toLowerCase(), content);
}
}
clientOutput.write("HTTP/1.1 200 OK".getBytes());
clientOutput.write(BREAK.getBytes());
Integer bytesLength = "hi".length();
String contentLengthBytes = "Content-Length:" + bytesLength;
clientOutput.write(contentLengthBytes.getBytes());
clientOutput.write(BREAK.getBytes());
clientOutput.write("Server: foo server".getBytes());
clientOutput.write(BREAK.getBytes());
clientOutput.write("Content-Type: text/html".getBytes());
clientOutput.write(DOUBLEBREAK.getBytes());
clientOutput.write("hi".getBytes());
clientOutput.close();
socketClient.close();
executors.execute(new NetworkRequestExecutor(serverSocket, executors));
} catch (IOException ex) {
ex.printStackTrace();
} catch (InterruptedException ioException) {
ioException.printStackTrace();
}
}
}
}
Run it:
gradle run
Browse to:
http://localhost:7654/