SocketChannel read returns 0 阻塞模式
SocketChannel read returns 0 in blocking mode
我有简单的客户端和服务器,客户端基于 NIO,而服务器是一个简单的老式程序。
我正在以默认阻塞模式使用客户端。在我尝试从客户端编写的程序中,服务器读取它。然后服务器回复,客户端读取。
我可以毫无问题地写入服务器,但事实证明客户端从服务器读取有问题。由于它处于阻塞模式,我希望根据文档它永远不会 returns 0。但事实并非如此,我总是将 client_channel.read 中的 return 视为 0。
*********************************服务器*************** ******************************
class MyBlockingServer extends Thread
{
private int M_PortNumber;
private ServerSocket M_ServerSocket;
MyBlockingServer(int PortNumber)
{
M_PortNumber = PortNumber;
try {
M_ServerSocket = new ServerSocket(M_PortNumber);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void run()
{
int my_number = 0;
while(true)
{
try {
Socket ClientServerTuple = M_ServerSocket.accept();
//System.out.println("Server address is "+ ClientServerTuple.getLocalAddress() + "Server Port is " + ClientServerTuple.getLocalPort());
//System.out.println("Client address is " + ClientServerTuple.getRemoteSocketAddress() + "Client address is" + ClientServerTuple.getPort());
DataInputStream inputStream = new DataInputStream(ClientServerTuple.getInputStream());
byte b[] = new byte[48];
inputStream.read(b);
System.out.println("[SERVER]" + new String(b));
DataOutputStream outputStream = new DataOutputStream(ClientServerTuple.getOutputStream());
byte c[] = new byte[100];
String output= new String("Thanks for connection, you suck tata" + " "+ my_number);
c = output.getBytes();
outputStream.write(c);
my_number++;
System.out.println("write done");
ClientServerTuple.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
void socket_close()
{
try {
M_ServerSocket.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
public class JavaBlocking
{
public static void main(String []args)
{
MyBlockingServer Server = new MyBlockingServer(8000);
try {
Server.start();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
*********************************客户*************** ******************************
public class JavaChannels
{
public static void main(String []args)
{
SocketChannel client_channel = null;
try {
client_channel = SocketChannel.open();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("[Async Client] Socket channel open");
try {
client_channel.connect(new InetSocketAddress("127.0.0.1",8000));
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("[Async Client] Socket channel connected");
ByteBuffer my_buffer = ByteBuffer.allocate(248);
try {
my_buffer.put("seven77".getBytes("UTF-8"));
} catch (UnsupportedEncodingException e2) {
// TODO Auto-generated catch block
e2.printStackTrace();
}
my_buffer.flip();
try {
int bytes_written = client_channel.write(my_buffer);
while(my_buffer.hasRemaining())
{
bytes_written = client_channel.write(my_buffer);
}
System.out.println("[Async Client] Wrote "+ bytes_written +" bytes");
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("[Async Client] Socket channel write finished");
my_buffer.clear();
my_buffer.flip();
try {
int read_length = client_channel.read(my_buffer);
System.out.println("Initial read is " + read_length + " bytes");
while(read_length !=-1)
{
read_length = client_channel.read(my_buffer);
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("Reading the buffer." +"Read "+read_length +"bytes");
}
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
System.out.println("[Async Client] server says" + new String(my_buffer.array()));
try {
client_channel.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
我从客户端看到的输出如下
Initial read is 0 bytes
Reading the buffer.Read 0bytes
Reading the buffer.Read 0bytes
Reading the buffer.Read 0bytes
我认为这是错误的:
System.out.println("[Async Client] Socket channel write finished");
my_buffer.clear();
my_buffer.flip();
clear
通过将位置设置为零并将限制设置为容量来准备读取缓冲区。
但是 flip
然后设置了位置限制;即零。这意味着当您尝试读入缓冲区时,零字节有 space。
去掉那个 flip
调用。
As it is in blocking mode, i expect that it never returns 0 according to the documentation.
哪个文档? SocketChannel.read(ByteBuffer)
的 javadocs 表示:
"It is guaranteed, however, that if a channel is in blocking mode and there is at least one byte remaining in the buffer then this method will block until at least one byte is read. "
在这种情况下,突出显示的条件为假。
我有简单的客户端和服务器,客户端基于 NIO,而服务器是一个简单的老式程序。
我正在以默认阻塞模式使用客户端。在我尝试从客户端编写的程序中,服务器读取它。然后服务器回复,客户端读取。
我可以毫无问题地写入服务器,但事实证明客户端从服务器读取有问题。由于它处于阻塞模式,我希望根据文档它永远不会 returns 0。但事实并非如此,我总是将 client_channel.read 中的 return 视为 0。
*********************************服务器*************** ******************************
class MyBlockingServer extends Thread
{
private int M_PortNumber;
private ServerSocket M_ServerSocket;
MyBlockingServer(int PortNumber)
{
M_PortNumber = PortNumber;
try {
M_ServerSocket = new ServerSocket(M_PortNumber);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void run()
{
int my_number = 0;
while(true)
{
try {
Socket ClientServerTuple = M_ServerSocket.accept();
//System.out.println("Server address is "+ ClientServerTuple.getLocalAddress() + "Server Port is " + ClientServerTuple.getLocalPort());
//System.out.println("Client address is " + ClientServerTuple.getRemoteSocketAddress() + "Client address is" + ClientServerTuple.getPort());
DataInputStream inputStream = new DataInputStream(ClientServerTuple.getInputStream());
byte b[] = new byte[48];
inputStream.read(b);
System.out.println("[SERVER]" + new String(b));
DataOutputStream outputStream = new DataOutputStream(ClientServerTuple.getOutputStream());
byte c[] = new byte[100];
String output= new String("Thanks for connection, you suck tata" + " "+ my_number);
c = output.getBytes();
outputStream.write(c);
my_number++;
System.out.println("write done");
ClientServerTuple.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
void socket_close()
{
try {
M_ServerSocket.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
public class JavaBlocking
{
public static void main(String []args)
{
MyBlockingServer Server = new MyBlockingServer(8000);
try {
Server.start();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
*********************************客户*************** ******************************
public class JavaChannels
{
public static void main(String []args)
{
SocketChannel client_channel = null;
try {
client_channel = SocketChannel.open();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("[Async Client] Socket channel open");
try {
client_channel.connect(new InetSocketAddress("127.0.0.1",8000));
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("[Async Client] Socket channel connected");
ByteBuffer my_buffer = ByteBuffer.allocate(248);
try {
my_buffer.put("seven77".getBytes("UTF-8"));
} catch (UnsupportedEncodingException e2) {
// TODO Auto-generated catch block
e2.printStackTrace();
}
my_buffer.flip();
try {
int bytes_written = client_channel.write(my_buffer);
while(my_buffer.hasRemaining())
{
bytes_written = client_channel.write(my_buffer);
}
System.out.println("[Async Client] Wrote "+ bytes_written +" bytes");
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("[Async Client] Socket channel write finished");
my_buffer.clear();
my_buffer.flip();
try {
int read_length = client_channel.read(my_buffer);
System.out.println("Initial read is " + read_length + " bytes");
while(read_length !=-1)
{
read_length = client_channel.read(my_buffer);
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("Reading the buffer." +"Read "+read_length +"bytes");
}
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
System.out.println("[Async Client] server says" + new String(my_buffer.array()));
try {
client_channel.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
我从客户端看到的输出如下
Initial read is 0 bytes
Reading the buffer.Read 0bytes
Reading the buffer.Read 0bytes
Reading the buffer.Read 0bytes
我认为这是错误的:
System.out.println("[Async Client] Socket channel write finished");
my_buffer.clear();
my_buffer.flip();
clear
通过将位置设置为零并将限制设置为容量来准备读取缓冲区。
但是 flip
然后设置了位置限制;即零。这意味着当您尝试读入缓冲区时,零字节有 space。
去掉那个 flip
调用。
As it is in blocking mode, i expect that it never returns 0 according to the documentation.
哪个文档? SocketChannel.read(ByteBuffer)
的 javadocs 表示:
"It is guaranteed, however, that if a channel is in blocking mode and there is at least one byte remaining in the buffer then this method will block until at least one byte is read. "
在这种情况下,突出显示的条件为假。