我正在编写一个简单的下载加速器。问题是我可以发送和接收一次消息。下次我尝试发送和接收消息时，我得不到来自服务器的响应。我甚至不确定我是否能够发送第二条消息。
第一条消息是这样的;
*HEAD /TIPS/LAWLER/PANOHOW2.PDF HTTP/1.0\r\n
HTTP/1.0\r\n
Connection: close\r\n
\r\n*
并且回复是;
*HTTP/1.1 200 OK
Date: Mon, 24 Jan 2011 10:53:38 GMT
Server: Apache
Last-Modified: Tue,
22 Sep 1998 13:19:52 GMT
ETag: "1968013-2b4f4-3386e15b6ee00"
Accept-Ranges: bytes
Content-Length: 177396
Connection: close
Content-Type: application/pdf*
当我试图传达信息时;
GET /TIPS/LAWLER/hedeh/PANOHOW2.PDF HTTP/1.0\r\n
Range: bytes=0-44349\r\n
Connection: close\r\n
\r\n
我一无所获。
我的代码出了什么问题？
public class Main {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
//Parse URL
String cmd = "http://www.imaging-resource.com"; //Host Name
if (cmd.contains("http://"))
{
cmd = cmd.substring(7); //
if (cmd.contains("/"))
{
int index = cmd.indexOf("/");
cmd = cmd.substring(0, index);
System.out.println(cmd);
}
}
String str = "HEAD /TIPS/LAWLER/PANOHOW2.PDF HTTP/1.0\r\nConnection: close\r\n\r\n"; //First message to send
//Create socket, connect, initialize read and write handlers
//in, out
Socket socket = null; //Create a client socket
SocketAddress sockaddr = null;
InetAddress address = null;
InputStream input = null; //Input handler
OutputStream output = null; //Output handler
try
{
address = InetAddress.getByName(cmd); //Get ip using host name
socket = new Socket(); //Contrusct Socket
sockaddr = new InetSocketAddress(address, 80);
//socket.setTcpNoDelay(false);
socket.connect(sockaddr, 2000); //Connect to server set and timeout to 2 sec
} //End of try Block
catch (Exception ex)
{
Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
System.out.println(ex);
} //End of catch Block
if (!socket.isConnected())
{
System.out.println("not connected");
System.exit(-1);
}
//Sending package here
try
{
int c;
byte[] buf = new byte[65535];
char[] chr = new char[65535];
input = socket.getInputStream(); //Input handler is created
output = socket.getOutputStream(); //Output handler is created
buf = str.getBytes(); //HEAD message converted into byte array
output.write(buf); //Sending message to server
output.flush();
int counter = 0;
while ((c = input.read()) != -1) //Reading received package
chr[counter++]=(char)c;
//input.reset();
str = new String(chr); //For better manipulation, server message is converted to string
System.out.println(str);
} catch (IOException e)
{
System.err.print(e);
} //End of catch
int index = str.indexOf("Content-Length"); //Look for "Content-Length" in response
str = str.substring(index); //Using its beginning index create an substring
index = str.indexOf("\r\n"); //Search for end of line
str = str.substring(0, index); //Erase end if line chars - \r\n
str = str.substring(16, str.length()); //"Content-Length: " 16 chars
int fileSize = Integer.parseInt(str); //Lentgh of file is converted to Integer
int[][] parts = new int[4][2]; //Beginning and en of jobs for threads will be stored here
int remainder = fileSize; //Bytes left to split for rest of the threads will be stored here
int start = 0;
int finish = 0;
for (int i = 0; i < 4; i++) //Number of threads many times
{
parts[i][0] = start; //*******Each threads job Interval(eg. 0-108)
//System.out.print(parts[i][0] + "-"); //******
finish += remainder / 4 - i; //*****
parts[i][1] = finish; //****
start = finish + 1; //***
if (i + 1 == 4)
parts[i][1] = fileSize; //*
}
str = "GET /TIPS/LAWLER/hedeh/PANOHOW2.PDF HTTP/1.0\r\nRange: bytes=" + parts[0][0] + "-" + parts[0][1] + "\r\nConnection: close\r\n\r\n";
//System.out.println(str);
if(!socket.isConnected())
{
System.out.println("closed");
try
{
socket.connect(sockaddr, 2000);
}//End od try
catch(Exception e){
System.err.print(e);
}//End of catch
}//End of If
System.out.println("Is Outputhandler closed :"+socket.isOutputShutdown());
System.out.println("Is Inputhandler closed :"+socket.isInputShutdown());
try
{
int c;
byte[] buf = new byte[65535];
char[] chr = new char[65535];
buf = str.getBytes(); //Output handler is created
output.write(buf); //Sending message to server
output.flush();
int counter = 0;
if((c = input.read()) != -1)
{
chr[counter++] = (char) c;
while ((c = input.read()) != -1) //Reading received package
{
System.out.println("response is not -1");
chr[counter++]=(char)c;
}
str = new String(chr); //For better manipulation, serve message is converted to string
System.out.println("Response "+str);
}//End of If
else System.out.println("No Response!");
}catch(Exception e)
{System.err.print(e);}
//Closing open stuff
try {
output.close();
input.close();
socket.close();
} catch (Exception e) {
System.out.println(e);
}
}// End of main method
}//End of class definition
答案 0 :(得分：4)
第一条消息是这样的;
HTTP/1.0\r\n
您必须使用HTTP版本1.1在单个TCP连接上使用多个请求。
在HTTP / 0.9和1.0中，连接在单个请求/响应对之后关闭。在HTTP / 1.1中引入了keep-alive-mechanism，其中连接可以被重用于多个请求。
另外，正如@Joachim Sauer在评论中指出的那样，你明确地在标题中说Connection: close。 ： - ）
答案 1 :(得分：1)
我认为问题在于您尝试使用普通TCP套接字连接到HTTP服务器。是的，HTTP在TCP之上，但它是复杂的协议，需要很多东西才能知道。我建议您使用更高级别的API来实现HTTP协议，并为您提供更方便的API。
最简单的例子是来自JDK的URL + URLConnection。来自雅加达的HttpClient可能更好。