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I understand that there are already alot of web server out there.
But i feel like creating one for learning purpose.
Is it something i should try to figure out and any guides or tutorials on this?
In java:
Create a ServerSocket and have this continually listen for connections - when a connection request comes in handle it by by parsing the HTTP request header, get the resource indicated and add some header information before sending back to the client. eg.
public class Server implements Runnable {
protected volatile boolean keepProcessing = true;
protected ServerSocket serverSocket;
protected static final int DEFAULT_TIMEOUT = 100000;
protected ExecutorService executor = Executors.newCachedThreadPool();
public Server(int port) throws IOException {
serverSocket = new ServerSocket(port);
serverSocket.setSoTimeout(DEFAULT_TIMEOUT);
}
#Override
public void run() {
while (keepProcessing) {
try {
Socket socket = serverSocket.accept();
System.out.println("client accepted");
executor.execute(new HttpRequest(socket));
} catch (Exception e) {
}
}
closeIgnoringException(serverSocket);
}
protected void closeIgnoringException(ServerSocket serverSocket) {
if (serverSocket != null) {
try {
serverSocket.close();
} catch (IOException ignore) {
}
}
}
public static void main(String[] args) {
ExecutorService executor = Executors.newCachedThreadPool();
try {
executor.execute(new WebServer(6789));
} catch (Exception e) {
e.printStackTrace();
}
}
}
final class HttpRequest implements Runnable {
final static String CRLF = "\r\n";
private Socket socket;
public HttpRequest(Socket socket) {
this.socket = socket;
}
public void run() {
try {
processRequest();
} catch (Exception e) {
System.out.println(e);
}
}
private void processRequest() throws Exception {
DataOutputStream os = new DataOutputStream(socket.getOutputStream());
BufferedReader br = new BufferedReader(new InputStreamReader(socket
.getInputStream()));
String requestLine = br.readLine();
System.out.println();
System.out.println(requestLine);
List<String> tokens = Arrays.asList(requestLine.split(" "));
Iterator<String> it = tokens.iterator();
it.next(); // skip over the method, which should be "GET"
String fileName = it.next();
fileName = "." + fileName;
FileInputStream fis = null;
boolean fileExists = true;
try {
fis = new FileInputStream(fileName);
} catch (FileNotFoundException e) {
fileExists = false;
}
String statusLine = null;
String contentTypeLine = null;
String entityBody = null;
String contentType = null;
if (fileExists) {
statusLine = "HTTP/1.0 200 OK";
contentType = contentType(fileName);
contentTypeLine = "Content-type: " + contentType + CRLF;
} else {
statusLine = "HTTP/1.0 404 NOT FOUND";
contentType = "text/html";
contentTypeLine = "Content-type: " + contentType + CRLF;
entityBody = "<HTML>" + "<HEAD><TITLE>Not Found</TITLE></HEAD>"
+ "<BODY>" + statusLine + " Not Found</BODY></HTML>";
}
os.writeBytes(statusLine);
os.writeBytes(contentTypeLine);
os.writeBytes(CRLF);
if (fileExists) {
sendBytes(fis, os);
fis.close();
} else {
os.writeBytes(entityBody);
}
String headerLine = null;
while ((headerLine = br.readLine()).length() != 0) {
System.out.println(headerLine);
}
os.close();
br.close();
socket.close();
}
private static void sendBytes(InputStream fis, DataOutputStream os)
throws Exception {
byte[] buffer = new byte[1024];
int bytes = 0;
while ((bytes = fis.read(buffer)) != -1) {
os.write(buffer, 0, bytes);
}
}
private static String contentType(String fileName) {
if (fileName.endsWith(".htm") || fileName.endsWith(".html")) {
return "text/html";
}
if (fileName.endsWith(".jpg") || fileName.endsWith(".jpeg")) {
return "image/jpeg";
}
if (fileName.endsWith(".gif")) {
return "image/gif";
}
if (fileName.endsWith(".txt")) {
return "text/plain";
}
if (fileName.endsWith(".pdf")) {
return "application/pdf";
}
return "application/octet-stream";
}
}
A Simple Webserver in C++ for Windows
Hope this helps you ; )
Alternatives
This project contains a modular web server in CodePlex
This article explains how to write a simple web server application using C# from CodeGuru
Start with understanding TCP/IP and the whole Internet protocol suite.
Then learn the HTTP 1.0 and 1.1 protocols.
That should start you on the way to understanding what you need to write in order to create a webserver from scratch.
Try asio from boost!
Boost.Asio is a cross-platform C++ library for network and low-level I/O programming that provides developers with a consistent asynchronous model using a modern C++ approach.
Most scripting language are capable and have plenty of examples on writing web servers. This route will give you a gentle introduction.
Related
From my Tomcat's servlet I execute an https connection to an external servlet.
This is the code:
HttpsURLConnection hpcon = null;
try {
URL url = new URL(surl);
hpcon = (HttpsURLConnection) url.openConnection();
hpcon.setRequestMethod("POST");
hpcon.setDoInput(true);
hpcon.setDoOutput(true);
hpcon.setUseCaches(false);
hpcon.setRequestProperty("Content-type", "application/x-www-form-urlencoded");
OutputStreamWriter wr = new OutputStreamWriter(hpcon.getOutputStream());
String params = "user=" + URLEncoder.encode(user, "UTF-8");
params += "&psswd=" + URLEncoder.encode(pssw, "UTF-8");
params += "&metodo=" + URLEncoder.encode(metodo, "UTF-8");
wr.write(params);
wr.flush();
wr.close();
hpcon.connect();
int respCode = hpcon.getResponseCode();
if (respCode == 200) {
BufferedReader br = new BufferedReader(new InputStreamReader(hpcon.getInputStream()));
String response = "";
String output;
while ((output = br.readLine()) != null) {
response += output;
}
if (response.indexOf("-") > 0) {
response = "-12";
System.out.println("ret = -12 - response = " + response);
}
br.close();
} else {
ret = "-11";
System.out.println("ret = -11 - respCode = " + respCode);
}
} catch (Exception e) {
e.printStackTrace();
ret = "-10";
System.out.println("ret = -10");
} finally {
if (hpcon != null) {
hpcon.disconnect();
}
}
Where surl is the full url of a servlet present in a different domain and the three parameters are read from a db table (the third really is fixed and is the operation that is make by the external servlet).
The result is:
ret = -11 - respCode = 404
Before make the connection I turn off the certificate's verify using the above code:
try {
TrustManager[] trustAllCerts = new TrustManager[]{new X509TrustManager() {
public java.security.cert.X509Certificate[] getAcceptedIssuers() {
return null;
}
public void checkClientTrusted(X509Certificate[] certs, String authType) {
}
public void checkServerTrusted(X509Certificate[] certs, String authType) {
}
}};
SSLContext sc = SSLContext.getInstance("SSL");
sc.init(null, trustAllCerts, new java.security.SecureRandom());
HttpsURLConnection.setDefaultSSLSocketFactory(sc.getSocketFactory());
HostnameVerifier allHostsValid = new HostnameVerifier() {
public boolean verify(String hostname, SSLSession session) {
return true;
}
};
HttpsURLConnection.setDefaultHostnameVerifier(allHostsValid);
} catch (Exception e) {
e.printStackTrace();
}
If I execute the same servlet manually from a browser with parameters in get mode all run correctly.
I tried to execute it on my code using the get mode and passing the three parameters in query string, but the result is the same.
How can I do to resolve the problem?
I have an android app which is making api requests to my server running Spring MVC. The RestController works fine when I make a request from the browser but it responds with 404 when I am making requests from android. Not sure why
Here is code snippet from Android app making requests
public class AsyncFetch extends AsyncTask<Pair<String, String>, String, String> {
public ProgressDialog pdLoading;
private HttpURLConnection conn;
private String urlStr;
private String requestMethod = "GET";
public AsyncFetch(String endpoint, Context ctx)
{
pdLoading = new ProgressDialog(ctx);
Properties reader = PropertiesReader.getInstance().getProperties(ctx, "app.properties");
String host = reader.getProperty("host", "10.0.2.2");
String port = reader.getProperty("port", "8080");
String protocol = reader.getProperty("protocol", "http");
String context = reader.getProperty("context", "");
this.urlStr = protocol+"://"+host+":"+port+context+endpoint;
}
#Override
protected void onPreExecute() {
super.onPreExecute();
//this method will be running on UI thread
pdLoading.setMessage("\tLoading...");
pdLoading.setCancelable(false);
pdLoading.show();
}
#Override
protected String doInBackground(Pair<String, String>... params) {
URL url;
try {
url = new URL(urlStr);
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return e.toString();
}
try {
conn = (HttpURLConnection) url.openConnection();
conn.setReadTimeout(READ_TIMEOUT);
conn.setConnectTimeout(CONNECTION_TIMEOUT);
conn.setRequestMethod(requestMethod);
conn.setDoOutput(true);
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
return e1.toString();
}
try {
int response_code = conn.getResponseCode();
// Check if successful connection made`enter code here`
if (response_code == HttpURLConnection.HTTP_OK) {
// Read data sent from server
InputStream input = conn.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(input));
StringBuilder result = new StringBuilder();
String line;
while ((line = reader.readLine()) != null) {
result.append(line);
}
// Pass data to onPostExecute method
return (result.toString());
} else {
return ("unsuccessful");
}
} catch (IOException e) {
e.printStackTrace();
return e.toString();
} finally {
conn.disconnect();
}
}
Spring MVC Controller
#RestController
public class ApiController {
#RequestMapping(value = "homefeed", method=RequestMethod.GET)
public String homefeed(#RequestParam(value="userId", required = false) Integer id, #RequestParam(value="search", required = false) String search, #RequestParam(value="page", required = false, defaultValue = "0") Integer page) { ... }
}
localhost:8080/api/homefeed -- works
127.0.0.1:8080/api/homefeed -- works
My Public IP:8080/api/homefeed -- does not works
10.0.2.2:8080/api/homefeed -- android emulator to localhost -- does not work
10.0.2.2:8080/Some resource other than the api endpoint -- works
Any help is highly appreciable, have wasted quiet some time in debugging.
How to redirect Glassfish server output into HttpServletResponse.out? I am making servlet in NetBeans.
here is a working example, just expose this as a servlet
public class ReadLogs extends HttpServlet {
private static final String CONTENT_TYPE = "text/html; charset=UTF-8";
public void init(ServletConfig config) throws ServletException {
super.init(config);
}
public void service(HttpServletRequest request,
HttpServletResponse response) throws ServletException,
IOException {
response.setContentType(CONTENT_TYPE);
PrintWriter out = response.getWriter();
out.append("<html>\n<head>\n\n");
out.append("<script>function toBottom()" + "{"
+ "window.scrollTo(0, document.body.scrollHeight);" + "}");
out.append("\n</script>");
out.append("\n</head>\n<body onload=\"toBottom();\">\n<pre>\n");
try {
File file = new File("C:\\pathToServerLogFile");
BufferedReader in = new BufferedReader(new FileReader(file));
StringBuilder sb = new StringBuilder();
while (in.ready()) {
String x = in.readLine();
sb.append(x).append("<br/>");
}
in.close();
out.append("\n</pre>\n</body>\n</html>");
out.close();
} catch (FileNotFoundException fnfe) {
fnfe.printStackTrace();
} catch (IOException ioe) {
ioe.printStackTrace();
}
}
}
UPDATE
If you need to print only the last portion of the file use this after line "in.close();"
//print only 1MB Oof data
if(sb.length()>1000000){
out.append(sb.substring(sb.length()-1000000, sb.length()));
}else{
out.append(sb.toString());
}
So.. to print only lines which appeared after invoking script I've made such code:
BufferedReader reader = new BufferedReader(new FileReader("/path/to/server/log/server.log"));
int lines = 0;
while (reader.readLine() != null) {
lines++;
}
reader.close();
BufferedReader reader2 = new BufferedReader(new FileReader("/path/to/server/log/server.log"));
String strLine;
int i = 0;
while (i != lines) {
reader2.readLine();
i++;
}
while ((strLine = reader2.readLine()) != null) {
out.println(stringToHTMLString(strLine));
out.println("<br>");
}
reader2.close();
When servlet starts it counts lines in server log (saves it in variable i), then after clicking on action form it read lines which indexes are higher than i and displays it on html page. I've used function stringToHTMLString which I found somewhere on stackoverflow.
Greets.
I want to know about implementing a "push" chat server, which uses HTTP keepalive headers. I just came to know two technologies such chat servers use - long polling, and push - but I could not get any concepts regarding what happens behind the scenes.
Can anyone please help me ? Any client side / server side code would be appreciated a lot !!
Here is some comet code from the Tomcat Docs (hhttp://tomcat.apache.org/tomcat-7.0-doc/aio.html)
public class ChatServlet
extends HttpServlet implements CometProcessor {
protected ArrayList<HttpServletResponse> connections =
new ArrayList<HttpServletResponse>();
protected MessageSender messageSender = null;
public void init() throws ServletException {
messageSender = new MessageSender();
Thread messageSenderThread =
new Thread(messageSender, "MessageSender[" + getServletContext().getContextPath() + "]");
messageSenderThread.setDaemon(true);
messageSenderThread.start();
}
public void destroy() {
connections.clear();
messageSender.stop();
messageSender = null;
}
/**
* Process the given Comet event.
*
* #param event The Comet event that will be processed
* #throws IOException
* #throws ServletException
*/
public void event(CometEvent event)
throws IOException, ServletException {
HttpServletRequest request = event.getHttpServletRequest();
HttpServletResponse response = event.getHttpServletResponse();
if (event.getEventType() == CometEvent.EventType.BEGIN) {
log("Begin for session: " + request.getSession(true).getId());
PrintWriter writer = response.getWriter();
writer.println("<!doctype html public \"-//w3c//dtd html 4.0 transitional//en\">");
writer.println("<head><title>JSP Chat</title></head><body bgcolor=\"#FFFFFF\">");
writer.flush();
synchronized(connections) {
connections.add(response);
}
} else if (event.getEventType() == CometEvent.EventType.ERROR) {
log("Error for session: " + request.getSession(true).getId());
synchronized(connections) {
connections.remove(response);
}
event.close();
} else if (event.getEventType() == CometEvent.EventType.END) {
log("End for session: " + request.getSession(true).getId());
synchronized(connections) {
connections.remove(response);
}
PrintWriter writer = response.getWriter();
writer.println("</body></html>");
event.close();
} else if (event.getEventType() == CometEvent.EventType.READ) {
InputStream is = request.getInputStream();
byte[] buf = new byte[512];
do {
int n = is.read(buf); //can throw an IOException
if (n > 0) {
log("Read " + n + " bytes: " + new String(buf, 0, n)
+ " for session: " + request.getSession(true).getId());
} else if (n < 0) {
error(event, request, response);
return;
}
} while (is.available() > 0);
}
}
public class MessageSender implements Runnable {
protected boolean running = true;
protected ArrayList<String> messages = new ArrayList<String>();
public MessageSender() {
}
public void stop() {
running = false;
}
/**
* Add message for sending.
*/
public void send(String user, String message) {
synchronized (messages) {
messages.add("[" + user + "]: " + message);
messages.notify();
}
}
public void run() {
while (running) {
if (messages.size() == 0) {
try {
synchronized (messages) {
messages.wait();
}
} catch (InterruptedException e) {
// Ignore
}
}
synchronized (connections) {
String[] pendingMessages = null;
synchronized (messages) {
pendingMessages = messages.toArray(new String[0]);
messages.clear();
}
// Send any pending message on all the open connections
for (int i = 0; i < connections.size(); i++) {
try {
PrintWriter writer = connections.get(i).getWriter();
for (int j = 0; j < pendingMessages.length; j++) {
writer.println(pendingMessages[j] + "<br>");
}
writer.flush();
} catch (IOException e) {
log("IOExeption sending message", e);
}
}
}
}
}
}
}
There are many specific techniques, generally now known under the name Comet. The Wikipedia article linked there is a pretty good intro.
Also see The Long Polling Technique.
This is the code that I am using for an HTTP connection:
HttpConnection connection = null;
// InputStream inputstream = null;
connection = (HttpConnection) Connector.open("http://www.google.com");
//HTTP Request
connection.setRequestMethod(HttpConnection.GET);
connection.setRequestProperty("Content-Type","//text plain");
connection.setRequestProperty("Connection", "close");
add(new LabelField(""+connection.getResponseMessage()));
connection.close();
This BlackBerry Development Guide titled "Code sample: Creating a connection over HTTP by using the first available transport" worked!!
ConnectionFactory connFact = new ConnectionFactory();
ConnectionDescriptor connDesc;
connDesc = connFact.getConnection("http://www.google.com");
if (connDesc != null) {
HttpConnection httpConn;
httpConn = (HttpConnection)connDesc.getConnection();
try {
final int iResponseCode = httpConn.getResponseCode();
UiApplication.getUiApplication().invokeLater(new Runnable() {
public void run() {
Dialog.alert("Response code: " +
Integer.toString(iResponseCode));
}
});
} catch (IOException e) {
System.err.println("Caught IOException: " + e.getMessage());
}
}