java.net.ConnectException：连接超时：没有更多信息
java.net.ConnectException: Connection timed out: no further information
今天我在不同的机器上测试服务器和客户端代码。
两者都在同一个 Wi-fi 网络上。
我使用以下代码创建了客户端，并在许多线程中遇到了这个异常：
java.net.ConnectException: Connection timed out: no further information
at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
at sun.nio.ch.SocketChannelImpl.finishConnect(Unknown Source)
at SocketTest.connect(Client.java:188)
at SocketTest.run(Client.java:73)
at java.lang.Thread.run(Unknown Source)
第 73 行是 connect(key)
第 188 行是 if(!(channel.finishConnect()))
所以客户端线程无法连接是因为没有来自服务器的回复？对吗？
问题）当我 运行 服务器和客户端都在同一台机器本地主机上时，不会出现此异常。可能是什么原因？ （网络问题？）。
此外，我还在 public void bind(SocketAddress endpoint,int backlog) 中使用 Backlog 队列参数作为 2000。虽然确切的大小未知（大约 200？），但我使用了一个很大的值，因此最大值值将被使用。（对吗？或 Java 将排队？）。
这可能是一个原因吗：服务器将请求放入积压队列，直到它有时间服务它，超时可能发生在客户端？
客户：
public class Client {
public static void main(String[] args) {
int n=100;
SocketTest [] st= new SocketTest[n];
for(int i=0;i<n;i++)
st[i]= new SocketTest("hi");
for(int i=0;i<n;i++)
{
if(i%50 == 0)
try{
Thread.sleep(5000);
}
catch(InterruptedException ie)
{
System.out.println(""+ie);
}
new Thread(st[i]).start();
}
}
}
class SocketTest implements Runnable {
private String message = "";
ByteBuffer readBuffer = ByteBuffer.allocate(1000);
private Selector selector;
private int i;
public static AtomicInteger cnt= new AtomicInteger(0);
public SocketTest(String message){
this.message = message;
}
@Override
public void run() {
SocketChannel channel;
try {
selector = Selector.open();
channel = SocketChannel.open();
channel.configureBlocking(false);
channel.register(selector, SelectionKey.OP_CONNECT);
channel.connect(new InetSocketAddress("192.168.1.10", 8511));
while (!Thread.currentThread().isInterrupted()){
selector.select();
Iterator<SelectionKey> keys = selector.selectedKeys().iterator();
while (keys.hasNext()){
SelectionKey key = keys.next();
keys.remove();
if (!key.isValid()) continue;
if (key.isConnectable()){
connect(key);
System.out.println("I am connected to the server");
}
if (key.isWritable()){
write(key);
}
if (key.isReadable()){
read(key);
}
}
}
}
catch(ClosedByInterruptException e)
{
// let go of thread
}
catch(CancelledKeyException e){
e.printStackTrace();
}
catch (IOException e1) {
System.out.println("IOE Occured|maybe Server died");
e1.printStackTrace();
} finally {
close();
}
}
private void close(){
try {
if(selector!=null)
selector.close();
}
catch(Exception e)
{
e.printStackTrace();
}
}
private void read (SelectionKey key) throws IOException {
SocketChannel channel = (SocketChannel) key.channel();
readBuffer.clear();
int length;
try{
length = channel.read(readBuffer);
} catch (IOException e){
System.out.println("Reading problem, closing connection for : "+channel.getLocalAddress());
key.cancel();
channel.close();
return;
}
if (length == -1){
System.out.println("Nothing was read from server");
channel.close();
key.cancel();
return;
}
readBuffer.flip();
byte[] buff = new byte[1024];
readBuffer.get(buff, 0, length);
//length=buff.length;
String fromserver = new String(buff,0,length,"UTF-8");
length = fromserver.length();
System.out.println("Server said: "+fromserver);
key.interestOps(SelectionKey.OP_WRITE);
}
private void write(SelectionKey key) throws IOException {
SocketChannel channel = (SocketChannel) key.channel();
i++;
message = "location now "+i;
if(i==2)
{
cnt.addAndGet(1);
System.out.println("****"+cnt.get()+"****");
}
try{
Thread.sleep(5000);
}
catch(InterruptedException ie)
{
System.out.println(""+ie);
//Thread.currentThread().interrupt();
}
//assuming all goes in one shot
channel.write(ByteBuffer.wrap(message.getBytes()));
key.interestOps(SelectionKey.OP_READ/*|SelectionKey.OP_WRITE*/);
}
private void connect(SelectionKey key){
SocketChannel channel= (SocketChannel) key.channel();
try
{
if(!(channel.finishConnect())){
//System.out.println("* Here *");
return;
}
}
catch(ConnectException e){
System.out.println("Conect Exception");
e.printStackTrace();
try{channel.close();}
catch(IOException ie){ie.printStackTrace();key.cancel();return;}
return;
}
catch(IOException e)
{
System.out.println("BP 1"+e);
e.printStackTrace();
try{channel.close();}
catch(IOException ie){ie.printStackTrace();key.cancel();return;}
return;
}
//channel.configureBlocking(false);
//channel.register(selector, SelectionKey.OP_WRITE);
key.interestOps(SelectionKey.OP_WRITE);
}
}
连接超时，因为服务器没有回复。
When I run both Server and Client on same machine localhost this exception does not arise. What may be the reasons ? (network problem ?).
为什么应该它出现？服务器在那里，客户端在那里，中间没有网络问题。这个问题没有意义。
Also I also use Backlog queue parameter in public void bind(SocketAddress endpoint,int backlog) as 2000. While exact size is unknown(around 200 ?) but I am using a large value so that maximum value will be used. Right?
没错。
or Java will make a queue?
我不知道这是什么意思。 Java 不对 backlog 参数做任何事情。它直接进入 TCP。
Can this be a reason: The Server puts the request in backlog queue and till it gets time to serve it, the timeout may have happened at Client ?
没有。只有 已完成 个连接进入积压队列。
今天我在不同的机器上测试服务器和客户端代码。 两者都在同一个 Wi-fi 网络上。
我使用以下代码创建了客户端，并在许多线程中遇到了这个异常：
java.net.ConnectException: Connection timed out: no further information
at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
at sun.nio.ch.SocketChannelImpl.finishConnect(Unknown Source)
at SocketTest.connect(Client.java:188)
at SocketTest.run(Client.java:73)
at java.lang.Thread.run(Unknown Source)
第 73 行是 connect(key)
第 188 行是 if(!(channel.finishConnect()))
所以客户端线程无法连接是因为没有来自服务器的回复？对吗？
问题）当我 运行 服务器和客户端都在同一台机器本地主机上时，不会出现此异常。可能是什么原因？ （网络问题？）。
此外，我还在 public void bind(SocketAddress endpoint,int backlog) 中使用 Backlog 队列参数作为 2000。虽然确切的大小未知（大约 200？），但我使用了一个很大的值，因此最大值值将被使用。（对吗？或 Java 将排队？）。
这可能是一个原因吗：服务器将请求放入积压队列，直到它有时间服务它，超时可能发生在客户端？
客户：
public class Client {
public static void main(String[] args) {
int n=100;
SocketTest [] st= new SocketTest[n];
for(int i=0;i<n;i++)
st[i]= new SocketTest("hi");
for(int i=0;i<n;i++)
{
if(i%50 == 0)
try{
Thread.sleep(5000);
}
catch(InterruptedException ie)
{
System.out.println(""+ie);
}
new Thread(st[i]).start();
}
}
}
class SocketTest implements Runnable {
private String message = "";
ByteBuffer readBuffer = ByteBuffer.allocate(1000);
private Selector selector;
private int i;
public static AtomicInteger cnt= new AtomicInteger(0);
public SocketTest(String message){
this.message = message;
}
@Override
public void run() {
SocketChannel channel;
try {
selector = Selector.open();
channel = SocketChannel.open();
channel.configureBlocking(false);
channel.register(selector, SelectionKey.OP_CONNECT);
channel.connect(new InetSocketAddress("192.168.1.10", 8511));
while (!Thread.currentThread().isInterrupted()){
selector.select();
Iterator<SelectionKey> keys = selector.selectedKeys().iterator();
while (keys.hasNext()){
SelectionKey key = keys.next();
keys.remove();
if (!key.isValid()) continue;
if (key.isConnectable()){
connect(key);
System.out.println("I am connected to the server");
}
if (key.isWritable()){
write(key);
}
if (key.isReadable()){
read(key);
}
}
}
}
catch(ClosedByInterruptException e)
{
// let go of thread
}
catch(CancelledKeyException e){
e.printStackTrace();
}
catch (IOException e1) {
System.out.println("IOE Occured|maybe Server died");
e1.printStackTrace();
} finally {
close();
}
}
private void close(){
try {
if(selector!=null)
selector.close();
}
catch(Exception e)
{
e.printStackTrace();
}
}
private void read (SelectionKey key) throws IOException {
SocketChannel channel = (SocketChannel) key.channel();
readBuffer.clear();
int length;
try{
length = channel.read(readBuffer);
} catch (IOException e){
System.out.println("Reading problem, closing connection for : "+channel.getLocalAddress());
key.cancel();
channel.close();
return;
}
if (length == -1){
System.out.println("Nothing was read from server");
channel.close();
key.cancel();
return;
}
readBuffer.flip();
byte[] buff = new byte[1024];
readBuffer.get(buff, 0, length);
//length=buff.length;
String fromserver = new String(buff,0,length,"UTF-8");
length = fromserver.length();
System.out.println("Server said: "+fromserver);
key.interestOps(SelectionKey.OP_WRITE);
}
private void write(SelectionKey key) throws IOException {
SocketChannel channel = (SocketChannel) key.channel();
i++;
message = "location now "+i;
if(i==2)
{
cnt.addAndGet(1);
System.out.println("****"+cnt.get()+"****");
}
try{
Thread.sleep(5000);
}
catch(InterruptedException ie)
{
System.out.println(""+ie);
//Thread.currentThread().interrupt();
}
//assuming all goes in one shot
channel.write(ByteBuffer.wrap(message.getBytes()));
key.interestOps(SelectionKey.OP_READ/*|SelectionKey.OP_WRITE*/);
}
private void connect(SelectionKey key){
SocketChannel channel= (SocketChannel) key.channel();
try
{
if(!(channel.finishConnect())){
//System.out.println("* Here *");
return;
}
}
catch(ConnectException e){
System.out.println("Conect Exception");
e.printStackTrace();
try{channel.close();}
catch(IOException ie){ie.printStackTrace();key.cancel();return;}
return;
}
catch(IOException e)
{
System.out.println("BP 1"+e);
e.printStackTrace();
try{channel.close();}
catch(IOException ie){ie.printStackTrace();key.cancel();return;}
return;
}
//channel.configureBlocking(false);
//channel.register(selector, SelectionKey.OP_WRITE);
key.interestOps(SelectionKey.OP_WRITE);
}
}
连接超时，因为服务器没有回复。
When I run both Server and Client on same machine localhost this exception does not arise. What may be the reasons ? (network problem ?).
为什么应该它出现？服务器在那里，客户端在那里，中间没有网络问题。这个问题没有意义。
Also I also use Backlog queue parameter in public void bind(SocketAddress endpoint,int backlog) as 2000. While exact size is unknown(around 200 ?) but I am using a large value so that maximum value will be used. Right?
没错。
or Java will make a queue?
我不知道这是什么意思。 Java 不对 backlog 参数做任何事情。它直接进入 TCP。
Can this be a reason: The Server puts the request in backlog queue and till it gets time to serve it, the timeout may have happened at Client ?
没有。只有 已完成 个连接进入积压队列。