Create a basic HTTP server in Java that answers browser requests and serves the requested page to the client, using the ServerSocket object.

1.import java.io.BufferedReader;
2.import java.io.File;
3.import java.io.FileReader;
4.import java.io.IOException;
5.import java.io.InputStreamReader;
6.import java.io.PrintWriter;
7.import java.net.ServerSocket;
8.import java.net.Socket;
9.import java.util.StringTokenizer;
10. 
11.public class BasicServer
12.{
13.        public static void main(String[] args)
14.        {
15.        final int SERVER_PORT = 1986;   
16.        ServerSocket serverSocket = null;
17.        String servPath = "src/pociu/cis201/server/wwwroot/";
18.       
19.        try
20.        {
21.            serverSocket = new ServerSocket(SERVER_PORT);
22.        }
23.        catch (IOException e)
24.        {
25.            System.err.println("Could not listen on port: " + SERVER_PORT);
26.            System.exit(1);
27.        }
28.       
29.        while (true)
30.        {
31.                Socket clientSocket = null;
32.                try
33.                {
34.                    clientSocket = serverSocket.accept();
35.                }
36.                catch (IOException e)
37.                {
38.                    System.err.println("Accept failed.");
39.                    System.exit(1);
40.                }
41.                PrintWriter out=null;
42.                BufferedReader in=null;
43.                try
44.                {
45.                        out = new PrintWriter(clientSocket.getOutputStream(), true);
46.                        in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
47.                        out.flush();
48.                       
49.                        String s;
50.                        while (!(s = in.readLine()).isEmpty())
51.                        {
52.                                if(s.length() > 0)
53.                                {
54.                                        StringTokenizer tokens = new StringTokenizer(s);
55.                                       
56.                                        // Unfortunately Java won't do Switch on strings...
57.                                        if(tokens.nextToken().equals("GET"))
58.                                        {
59.                                                String fileRequested = tokens.nextToken().replace("/", "");
60.                                                //Remove the query string before attempting to retrieve the file from the file system
61.                                                fileRequested = RemoveQString(fileRequested);
62.                                                if(fileRequested.equals("")) // If the root is requested
63.                                                {
64.                                                        fileRequested = "index.html"; // Show the index.html page
65.                                                }
66.                                                File reqFile = new File(servPath + fileRequested);
67.                                                System.out.println("File " + fileRequested + " was requested.");
68.                                                if(reqFile.exists())
69.                                                {
70.                                                        try
71.                                                        {
72.                                                                FileReader fText = new FileReader(reqFile);
73.                                                                BufferedReader bfFile = new BufferedReader(fText);
74.                                                               
75.                                                                String line;
76.                                                                while ((line = bfFile.readLine()) != null)
77.                                                                {
78.                                                                        out.write(line);
79.                                                                }
80.                                                                out.flush();
81.                                                                bfFile.close();
82.                                                                System.out.println("The file was served.");
83.                                                        }
84.                                                        catch(IOException e)
85.                                                        {
86.                                                                out.write("The file you have requested (" + fileRequested + ") could not be served: " + e.getMessage());
87.                                                                out.flush();
88.                                                                System.out.println("An IO exception occured.");
89.                                                        }
90.                                                }
91.                                                else
92.                                                {
93.                                                        out.write("The file you have requested (" + fileRequested + ") was not found.");
94.                                                        out.flush();
95.                                                        System.out.println("File not found.");
96.                                                }
97.                                        }
98.                                }
99.                        }
100.                        out.close();
101.                        in.close();
102.                        clientSocket.close();
103.                }
104.                catch (IOException e)
105.                {
106.                        e.printStackTrace();
107.                }
108.        }
109.    }
110.       
111.        private static String RemoveQString(String str)
112.        {
113.                int qPos = str.indexOf("?");
114.                if(qPos >= 0)
115.                {
116.                        str = str.substring(0, qPos);
117.                }
118.                return str;
119.        }
120.}