我的编程任务要求我在客户端和服务器之间创建代理。 我的客户端通过代理向服务器发出请求，然后代理转发它并将响应从服务器返回给客户端。
以下是我采取的步骤：
1）从客户端获取请求并将请求数据存储到字节数组
2）使用缓冲读取器从字节数组中读取
3）从Host：header字段获取主机名，并用它创建一个serverSocket
4）将请求数据转发到serverSocket输出流
5）将来自serverSocket输入流的响应数据检索到另一个字节数组
6）将字节数组中的内容写入clientSocket输出流
但是，在步骤6之后，浏览器无法显示响应数据。有什么帮助吗？
import java.io.*;
import java.net.*;
import java.util.*;
public class proxy2 {
public static void main(String args[]) throws Exception
{
int port = Integer.parseInt(args[0]);
File fileSub= new File(args[1]); //fileSub
File fileRediect = new File(args[2]); //fileRedirect
ServerSocket listener = new ServerSocket(port);
while (true) {
proxy_func(listener.accept());
}
}
public static void proxy_func(Socket clientSocket) throws Exception{
OutputStream outputToClient = clientSocket.getOutputStream();
//store clientSocket's inputstream into a buffer
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
int nRead; //start offset in the data
byte[] data = new byte[16384]; //create byte array
//read each byte from InputStream and write it to a ByteArrayOutputStream
while((nRead = clientSocket.getInputStream().read(data, 0, data.length)) != -1) {
buffer.write(data, 0, nRead);
}
buffer.flush(); //forces any buffered bytes to be written out
data = buffer.toByteArray(); //retrieve the underlying byte array
System.out.println(new String(data));
//create buffer reader for clientSocket's inputstream
InputStream inputStream = new ByteArrayInputStream(data);
BufferedReader readFromClient = new BufferedReader(new InputStreamReader(inputStream));
String[] strArr;
String line;
String hostname = null;
//get hostname
while( (line=readFromClient.readLine()) != null)
{
strArr = line.split(" ");
if(strArr[0].equals("Host:"))
hostname = strArr[1];
}
System.out.println("Host: " + hostname);
//create server socket
Socket serverSocket = new Socket(hostname, 80);
OutputStream outputToServer = serverSocket.getOutputStream();
InputStream inputFromServer = serverSocket.getInputStream();
//forward request to server
System.out.println("forward request to server...");
outputToServer.write(data);
//receive data from server and write response back to client
byte[] receivedData = new byte[16384];
int size;
while((size = inputFromServer.read(receivedData)) != -1)
{
System.out.println("write response back to client...");
System.out.println("size: " + size);
System.out.println(new String(receivedData));
outputToClient.write(receivedData, 0, size);
}
System.out.println("flushing...");
outputToClient.flush();
outputToClient.close();
}
}
所以基本上我遵循I / O的这种布局：
{
OutputStream outputToClient = clientSocket.getOutputStream();
BufferedReader readFromClient = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
//step 1
//get the HTTP request header from your firefox
String line = readFromClient.readLine();
//if the Content_Length within the HTTP header exists and not equals to 0
char [] buffer = new char [#];
readFromClient.read(buffer, 0, Content_Length); //get the body message
OutputStream outputToServer = serverSocket.getOutputStream();
InputStream inputFromServer = serverSocket.getInputStream();
//step 2
outputToServer.write(Bytes[]) //forword the HTTP requests to server host.
//step 3
byte[] data = new byte[#];
while ((size = inputFromServer.read(data)) != -1) //get the response data from server
{
//step 4
outputToClient.write(data, 0, size); //forward the data to your firefox
}
}
答案 0 :(得分：1)
最后一部分存在问题：
byte[] receivedData = new byte[16384];
int size;
while((size = inputFromServer.read(receivedData)) != -1)
{
System.out.println("write response back to client...");
System.out.println("size: " + size);
System.out.println(new String(receivedData));
}
outputToClient.write(receivedData);
所以，假设服务器发送回100万字节。循环通过16384字节的块读取它们，一旦它读取了所有块，它就会在最后一次读取之后发送回receivedData缓冲区中剩余的内容。因此，浏览器只会在服务器发送的1,000,000个字节中收到16384个字节。
您必须将从服务器读取的所有内容发送到浏览器：
byte[] receivedData = new byte[16384];
int size;
while((size = inputFromServer.read(receivedData)) != -1)
{
System.out.println("write response back to client...");
System.out.println("size: " + size);
System.out.println(new String(receivedData));
outputToClient.write(receivedData, 0, size);
}
答案 1 :(得分：0)
好的，我发现了问题的原因。我的while循环被阻止，因为我没有检测到HTTP请求的结束。这个答案简洁地解决了我的问题：https://stackoverflow.com/a/9542710
只是在这里张贴那些偶然发现这个问题并迷路的人。
这是我可以使用的更新代码（注意我添加了一个检测HTTP请求结束的方法）：
import java.io.*;
import java.net.*;
import java.util.*;
public class proxy2 {
public static void main(String args[]) throws Exception
{
int port = Integer.parseInt(args[0]);
File fileSub= new File(args[1]); //fileSub
File fileRediect = new File(args[2]); //fileRedirect
//create listener socket to listen for requests from browser
ServerSocket listener = new ServerSocket(port);
while (true) {
proxy_func(listener.accept());
}
}
public static void proxy_func(Socket clientSocket) throws Exception{
OutputStream outputToClient = clientSocket.getOutputStream();
InputStream inputFromClient = clientSocket.getInputStream();
//store clientSocket's inputstream into a buffer
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
int nRead; //start offset in the data
byte[] data = new byte[16384];
//read each byte from InputStream and write it to a ByteArrayOutputStream
while((nRead = inputFromClient.read(data, 0, data.length)) != -1) {
System.out.println("reading from client...");
buffer.write(data, 0, nRead);
//if reached end of HTTP request, break out of this loop
if(endOfRequest(data) == true)
break;
}
buffer.flush(); //forces any buffered bytes to be written out
data = buffer.toByteArray(); //retrieve the underlying byte array
System.out.println(new String(data));
//create buffered reader for byte array input stream (request data)
InputStream inputStream = new ByteArrayInputStream(data);
BufferedReader readFromClient = new BufferedReader(new InputStreamReader(inputStream));
String[] strArr;
String line;
String hostname = null;
//get hostname
while( (line=readFromClient.readLine()) != null)
{
strArr = line.split(" ");
if(strArr[0].equals("Host:"))
hostname = strArr[1];
}
System.out.println("Host: " + hostname);
//create server socket
Socket serverSocket = new Socket(hostname, 80);
OutputStream outputToServer = serverSocket.getOutputStream();
//InputStream inputFromServer = serverSocket.getInputStream();
//forward request to server
System.out.println("forward request to server...");
outputToServer.write(data);
//receive data from server and write response back to client
DataInputStream inputFromServer = new DataInputStream(serverSocket.getInputStream());
byte[] receivedData = new byte[1024];
int size;
while((size = inputFromServer.read(receivedData, 0, receivedData.length)) != -1)
{
System.out.println("write response back to client...");
System.out.println(new String(receivedData));
outputToClient.write(receivedData, 0, size);
outputToClient.flush();
}
System.out.println("done sending");
outputToClient.close();
}
//method to detect end of HTTP request
//return true if detected, otherwise false
public static boolean endOfRequest(byte[] data) throws Exception
{
System.out.println("parsing request..");
BufferedReader br = new BufferedReader(new InputStreamReader(new ByteArrayInputStream(data)));
String line;
while( (line=br.readLine()) != null) {
if (line.equals(""))
return true;
}
return false;
}
}
答案 2 :(得分：0)
你这样做是错的。 HTTP代理只需要读取CONNECT命令并对其进行操作。之后，您只需要尽快同时复制两个方向的字节。您尝试理解代理中的HTTP协议越多，您将引入的错误就越多。