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Reading from a socket using buffered reader blocks [duplicate]

This question already has answers here:
Buffered Reader HTTP POST
(4 answers)
Closed 7 years ago.
I am trying to create a http server in java.
The following is a fragment of my code.
ServerSocket s = new ServerSocket(80);
while(true){
Socket client = s.accept();
BufferedReader in = new BufferedReader(
new InputStreamReader(client.getInputStream()));
String input = in.readLine(), ff;
System.out.println(input);
while((ff = in.readLine()) != null){
System.out.println(ff);
}
System.out.println("asd");
in.close();
client.close();
}
Asd is never printed. When I try to do a POST on the local host, it sends me all the headers but doesn't send any content data. It just waits there doing nothing.
I am doing a post using Jquery
$.post("http://127.0.0.1/",
{
name: "Donald Duck",
city: "Duckburg"
},
function(data,status){
alert("Data: " + data + "\nStatus: " + status);
});
This is what is being printed on the screen:
POST / HTTP/1.1
Host: 127.0.0.1
Connection: keep-alive
Content-Length: 5
Accept: */*
Origin: http://www.w3schools.com
User-Agent: Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.36 (KHTML, like Gecko) Ubuntu Chromium/47.0.2526.73 Chrome/47.0.2526.73 Safari/537.36
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
That's it, nothing after this. It waits indefinitely at this point.

My guess would be that your actual content/payload is not terminated by the expected line delimiters as described in BufferedReader#readLine().
This blocks your in.readLine() invocation.
I would try to use the read() method instead and see if that helps. As in
while((value = in.read()) != -1) {
char c = (char)value;
System.out.println(c);
}
Edit: In fact, your question most likely duplicates this question: Buffered Reader HTTP POST

Extracting the body from HTTP post requestH

I have a weird problem when trying to extract the body of a given
HTTP post request.
If I try to extract only the header, it works fine. When I try to extract the body, the method blocks (even thought the stream still has data in it).
Here is my code:
private void extractHeader() throws Exception {
StringBuffer buffer = new StringBuffer();
InputStreamReader reader = new InputStreamReader(socket.getInputStream());
BufferedReader bufferedReader = new BufferedReader(reader);
boolean extractBody = false;
int bodyLength = 0;
String line;
while (!(line = bufferedReader.readLine()).equals("")) {
buffer.append(line + "");
if (line.startsWith("POST")) {
extractBody = true;
}
if (line.startsWith("Content-Length:")) {
bodyLength = Integer.valueOf(line.substring(line.indexOf(' ') + 1, line.length()));
}
}
requestHeader = buffer.toString();
if (extractBody) {
char[] body = new char[bodyLength];
reader.read(body, 0, bodyLength);
requestBody = new String(body);
}
}
And this is the request request:
POST /params_info.html HTTP/1.1
Host: localhost:8080
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:42.0) Gecko/20100101 Firefox/42.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: http://localhost:8080/index.html
Connection: keep-alive
Content-Type: application/x-www-form-urlencoded
Content-Length: 31
firstname=Mickey&lastname=Mouse
From what I understand, the loop will go until seeing the empty string
and then stoping. At this stage, the reader can read 'Content-Length' number of bytes. So it should have no problem reading the body and finish. Instead, it blocks on the line 'reader.read(body, 0, bodyLength);'
(The reason I don't use readLine() is because body does not end with \n).
I've tried debugging it in al kinds of ways but I get nothing. Can anyone please help with this?

You're reading the header using the bufferedReader:
while (!(line = bufferedReader.readLine()).equals("")) {
but read the body using reader, which has no data available, as this has been read and buffered by the bufferedReader:
reader.read(body, 0, bodyLength);
Change that line to
bufferedReader.read(body, 0, bodyLength);

Java HTTP Server response incomplete

I am trying to build my own embedded HTTP Server for Java with very specific usage for an internal closed system. Using embedded solution that already exists meant that I need to strip them down to refit them for my internal system's specific use cases.
I have managed to get my Java HTTPD receive HTTP Requests from web browsers but the Requests that the HTTPD receives are incomplete.
Below is the server thread codes (pretending the ServerSocket works perfectly fine):
public class HttpThread implements Runnable {
private Socket socket;
private DataInputStream in;
private PrintStream out;
private BufferedReader br;
private String EOF = "\n";
private String STATUS_200 = "HTTP/1.1 200 OK" + EOF;
public HttpThread(Socket socket) throws IOException {
this.socket = socket;
this.in = new DataInputStream(this.socket.getInputStream());
this.out = new PrintStream(new BufferedOutputStream(this.socket.getOutputStream()));
}
#Override
public void run() {
System.out.println("New thread...");
try {
processInput();
//socket.close();
} catch (IOException ex) {
Logger.getLogger(HttpThread.class.getName()).log(Level.SEVERE, null, ex);
} finally {
if (br != null) {
try {
br.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
//System.out.println("Thread END...");
}
private String processInput() throws IOException {
String line;
StringBuilder buff = new StringBuilder();
br = new BufferedReader(new InputStreamReader(in));
while ((line = br.readLine()) != null) {
buff.append(line);
System.out.println(">>> " + line);
if (line.trim().isEmpty()) {
break;
}
}
out.print(STATUS_200);
out.print("Server: Test Server\n" +
"Content-Type: text/html; charset=UTF-8\n" +
"Connection: close");
out.print(EOF);
out.print("<html><body>yello</body></html>");
out.print(EOF);
out.flush();
System.out.println(STATUS_200);
return buff.toString();
}
}
I am using this HTML Script to test the server thread to simulate a POST request:
<html>
<body onLoad="document.test.submit();">
<form action="http://localhost:9999/" method="POST" name="test">
<input type=hidden name="userid" value="1443"/>
<input type=hidden name="password" value="1443"/>
</form>
</body>
</html>
When I use the browser to call the HTML codes the Java HTTPD receives an incomplete response:
New thread...
>>> POST / HTTP/1.1
>>> Host: localhost:9999
>>> Connection: keep-alive
>>> Content-Length: 25
>>> Cache-Control: max-age=0
>>> Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
>>> Origin: null
>>> User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/28.0.1500.72 Safari/537.36
>>> Content-Type: application/x-www-form-urlencoded
>>> Accept-Encoding: gzip,deflate,sdch
>>> Accept-Language: en-GB,en-US;q=0.8,en;q=0.6
>>>
HTTP/1.1 200 OK
New thread...
>>> GET /favicon.ico HTTP/1.1
>>> Host: localhost:9999
>>> Connection: keep-alive
>>> Accept: */*
>>> User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/28.0.1500.72 Safari/537.36
>>> Accept-Encoding: gzip,deflate,sdch
>>> Accept-Language: en-GB,en-US;q=0.8,en;q=0.6
>>>
HTTP/1.1 200 OK
It seems that the HTTPD only received the HTTP headers and stopped receiving the POST body.
May I know of some solutions to solve the above problem ?
Thanks.

The HTTP headers and body are separated by an empty line (also see the HTTP RFC, especially the chapter "5 Request"). Your server reads the socket Inputstream but breaks on an empty line :
if (line.trim().isEmpty()) {
break;
}
Therefore obviously you will not receive the body. You should fully consume the Inputstream instead.
Besides that, I would advise you to use already existing solutions. There is an abundance of HTTP server implementations, that are well tested and proven in real world usage. Save yourself alot of headache and use an existing lightweight server like e.g. Jetty, Netty or similar ones.

I switched out the while loop that does the readline() with the following code:
int i;
byte[] buffer = new byte[2048];
i = in.read(buffer);
for (int j = 0; j < i; j++) {
buff.append((char) buffer[j]);
}
System.out.println(buff.toString());
and the problem is solved.
Pyranja, thanks for the help.
Thanks to http://kcd.sytes.net/articles/simple_web_server.php IF you follow concisely. Somehow the br.readline() is not fully reading the lines properly after the empty line.
The code fragment should now look like:
private String processInput() throws IOException {
String line;
StringBuilder buff = new StringBuilder();
int i;
byte[] buffer = new byte[2048];
i = in.read(buffer);
for (int j = 0; j < i; j++) {
buff.append((char) buffer[j]);
}
System.out.println(buff.toString());
out.print(STATUS_200);
out.print("Server: Test Server\n" +
"Content-Type: text/html; charset=UTF-8\n" +
"Connection: close");
out.print(EOF);
out.print("<html><body>yello</body></html>");
out.print(EOF);
out.flush();
System.out.println(STATUS_200);
return buff.toString();
}
I guess it's a good experience learning how to build a simple HTTP Server :D .

How to make reading client request module very efficient (HTTP)?

I am building my HTTP WEB SERVER . In this project I made one module that reads clients request, but that is very inefficient. So please suggest some suggestion, how can I make this module very efficient. I am sharing my code that performs reading request task. See below,
Waiting for your suggestions. THanks in advance.
Part of my code
final static int BUF_SIZE = 2048;
byte[] buf = new byte[BUF_SIZE];
private Socket s;
InputStream is = new BufferedInputStream(s.getInputStream());
int nread = 0, r = 0;
outerloop:
while (nread < BUF_SIZE) {
r = is.read(buf, nread, BUF_SIZE - nread);
if (r == -1) {
/* EOF */
return;
}
int i = nread;
nread += r;
for (; i < nread; i++) {
if (buf[i] == (byte) '\n' || buf[i] == (byte) '\r') {
/* read one line */
break outerloop;
}
}
}
EDIT NO. 1
Below is the request from client, that is stored in is
GET / HTTP/1.1
Host: localhost:8080
Connection: keep-alive
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.64 Safari/537.31
Accept-Encoding: gzip,deflate,sdch
Accept-Language: en-US,en;q=0.8
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
This is end by special character \r or \n.
How can I put this in buffer using any optimized method.

If you want to speed up everything, i would consider switching from java.io to java.nio.
Further Information:
http://en.wikipedia.org/wiki/New_I/O
or just google it ;)

If you're reading lines, use BufferedReader.readLine(). At present you're processing every character twice. But I see no reason to think there is any major inefficiency here, considering the entire process will be network-bound.

XMLHttpRequest java javascript

I try to communicate between javascript and java. My script javascript send a message to java and java send a response.
javascript part:
var xmlhttp = new XMLHttpRequest();
xmlhttp.onreadystatechange=function()
{
if (xmlhttp.readyState==4)
{
alert(xmlhttp.responseText);
}
}
var s = "LIGNE \n 2 \n il fait beau \nEND\n";
xmlhttp.open("POST","http://localhost:6020",true);
xmlhttp.send(s);
java part:
try {
serverSocket = new ServerSocket(6020);
} catch (IOException e) {
System.err.println("Could not listen on port: 6020.");
System.exit(-1);
}
serverSocket.accept()
BufferedReader br = new BufferedReader(
new InputStreamReader(socket.getInputStream()));
BufferedWriter bw = new BufferedWriter(
new OutputStreamWriter(socket.getOutputStream()));
String ligne = "";
while(!(ligne = plec.readLine()).equals("END")){
System.out.println(ligne);
}
bw.write("Il fait beau\n");
bw.flush();
bw.close();
plec.close();
socket.close();
output java :
POST / HTTP/1.1
Host: localhost:6020
User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:13.0) Gecko/20100101 Firefox/13.0.1
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: fr,fr-fr;q=0.8,en-us;q=0.5,en;q=0.3
Accept-Encoding: gzip, deflate
Connection: keep-alive
Referer: http://localhost:8080/test.html
Content-Length: 30
Content-Type: text/plain; charset=UTF-8
Origin: http://localhost:8080
Pragma: no-cache
Cache-Control: no-cache
LIGNE
2
il fait beau
So, I receive correctly the message send by javascript but the alert his always empty. How to response at this message?
I try a lot of possiblity but they don't work. And I don't want to use the servlet, it's to heavy to do that.
Thanks.
Edit:
I did this :
bw.write("HTTP/1.1 200 OK\r\n"+
"Content-Type: text/html; charset=utf-8\r\n"+
"Content-Length: 13\r\n\r\n" +
"il fait beau\n");
and this:
String data = "il fait beau \n";
StringBuilder builder = new StringBuilder();
builder.append("HTTP/1.1 200 OK\r\n");
builder.append("Content-Type: text/html; charset=utf-8\r\n");
builder.append("Content-Length:" + data.length() + "\r\n\r\n");
builder.append(data);
bw.write(builder.toString());
But the alert remain empty. Maybe it's a problem in the javascript.

The javascript needs to see a full HTTP response. Merely sending back characters to it, makes it discard the reply as it is an invalid HTTP response.
In your java code, send back something like this
HTTP/1.1 200 OK
Content-Type: text/html; charset=utf-8
Content-Length: <length of data>
---data here---
Reference
Something like:
StringBuilder builder = new StringBuilder();
builder.append("HTTP/1.1 200 OK\r\n");
builder.append("Content-Type: text/plain; charset=utf-8\r\n");
builder.append("Content-Length:" + data.length() + "\r\n\r\n);
builder.append(data);
bw.write(builder.toString());

Try:
bw.write("HTTP/1.1 200 OK\r\n"+
"Content-Type: text/html; charset=utf-8\r\n"+
"Content-Length: 13\r\n\r\n" +
"il fait beau\n");
HTTP-Headers are separated by \r\n (CRLF). Headers and body is spearated by \r\n\r\n.
Note that you set the length to 13 because you also have to count the \n at the end of your string.
EDIT: It does not work because of the cross-domain-policy. http://localhost:6020 is not the same port as the website which executes your JavaScript and so the xmlhttprequest might not be delivered.