This question already has answers here:
Java - Connecting a client to a server without the localhost
（2个答案）
5年前关闭。
嗨，有人在这里问过类似的问题：Can't connect to my server when I put in my IP in Java
但是我有一个不同的错误。我是Java的新手，请阅读oracle的教程代码，尝试并学习如何设置客户端/服务器。
通过cmd运行的程序如下所示：
在“ java KnockKnockClient localhost 4444”行上，它设置主机和端口号。本地主机或127.0.0.1可以工作，但是如果我用IP地址替换它，则会收到此错误：
无法获得与[我的IP地址]的连接的I / O
我尝试在关闭防火墙的情况下执行此操作，但此操作无效。我真正想做的是将KnockKnockServer程序放在我的家用计算机上，将KnockKnockClient程序放在任何其他计算机上，并且无论该另一台计算机在哪里，都可以使用Client程序连接到服务器。我究竟做错了什么？谢谢。
我添加了printStackTrace（）：
我猜这意味着未建立连接。我尝试在路由器设置上打开端口，但仍然无法正常工作。我有一台Cisco Linksys E2000路由器，是否只是不允许这些端口打开？
（2个答案）
5年前关闭。
嗨，有人在这里问过类似的问题：Can't connect to my server when I put in my IP in Java
但是我有一个不同的错误。我是Java的新手，请阅读oracle的教程代码，尝试并学习如何设置客户端/服务器。
/*
* Copyright (c) 1995, 2013, Oracle and/or its affiliates. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of Oracle or the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
import java.io.*;
import java.net.*;
public class KnockKnockClient {
public static void main(String[] args) throws IOException {
if (args.length != 2) {
System.err.println(
"Usage: java EchoClient <host name> <port number>");
System.exit(1);
}
String hostName = args[0];
int portNumber = Integer.parseInt(args[1]);
try (
Socket kkSocket = new Socket(hostName, portNumber);
PrintWriter out = new PrintWriter(kkSocket.getOutputStream(), true);
BufferedReader in = new BufferedReader(
new InputStreamReader(kkSocket.getInputStream()));
) {
BufferedReader stdIn =
new BufferedReader(new InputStreamReader(System.in));
String fromServer;
String fromUser;
while ((fromServer = in.readLine()) != null) {
System.out.println("Server: " + fromServer);
if (fromServer.equals("Bye."))
break;
fromUser = stdIn.readLine();
if (fromUser != null) {
System.out.println("Client: " + fromUser);
out.println(fromUser);
}
}
} catch (UnknownHostException e) {
System.err.println("Don't know about host " + hostName);
System.exit(1);
} catch (IOException e) {
System.err.println("Couldn't get I/O for the connection to " +
hostName);
System.exit(1);
}
}
}
/*
* Copyright (c) 1995, 2014, Oracle and/or its affiliates. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of Oracle or the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
import java.net.*;
import java.io.*;
public class KnockKnockServer {
public static void main(String[] args) throws IOException {
if (args.length != 1) {
System.err.println("Usage: java KnockKnockServer <port number>");
System.exit(1);
}
int portNumber = Integer.parseInt(args[0]);
try (
ServerSocket serverSocket = new ServerSocket(portNumber);
Socket clientSocket = serverSocket.accept();
PrintWriter out =
new PrintWriter(clientSocket.getOutputStream(), true);
BufferedReader in = new BufferedReader(
new InputStreamReader(clientSocket.getInputStream()));
) {
String inputLine, outputLine;
// Initiate conversation with client
KnockKnockProtocol kkp = new KnockKnockProtocol();
outputLine = kkp.processInput(null);
out.println(outputLine);
while ((inputLine = in.readLine()) != null) {
outputLine = kkp.processInput(inputLine);
out.println(outputLine);
if (outputLine.equals("Bye."))
break;
}
} catch (IOException e) {
System.out.println("Exception caught when trying to listen on port "
+ portNumber + " or listening for a connection");
System.out.println(e.getMessage());
}
}
}
通过cmd运行的程序如下所示：
Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation. All rights reserved.
C:\Users\FRYS ELECTRONICS>java KnockKnockServer 4444
C:\Users\FRYS ELECTRONICS>
Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation. All rights reserved.
C:\Users\FRYS ELECTRONICS>java KnockKnockClient localhost 4444
Server: Knock! Knock!
Who's there?
Client: Who's there?
Server: Turnip
Turnip who?
Client: Turnip who?
Server: Turnip the heat, it's cold in here! Want another? (y/n)
n
Client: n
Server: Bye.
C:\Users\FRYS ELECTRONICS>
在“ java KnockKnockClient localhost 4444”行上，它设置主机和端口号。本地主机或127.0.0.1可以工作，但是如果我用IP地址替换它，则会收到此错误：
无法获得与[我的IP地址]的连接的I / O
我尝试在关闭防火墙的情况下执行此操作，但此操作无效。我真正想做的是将KnockKnockServer程序放在我的家用计算机上，将KnockKnockClient程序放在任何其他计算机上，并且无论该另一台计算机在哪里，都可以使用Client程序连接到服务器。我究竟做错了什么？谢谢。
我添加了printStackTrace（）：
java.net.ConnectException: Connection timed out: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.<init>(Unknown Source)
at java.net.Socket.<init>(Unknown Source)
at KnockKnockClient.main(knockknockclient.java:48)
我猜这意味着未建立连接。我尝试在路由器设置上打开端口，但仍然无法正常工作。我有一台Cisco Linksys E2000路由器，是否只是不允许这些端口打开？
最佳答案
查看KnockKnockClient类的最后几行。之所以打印该错误，是因为您发布的代码告诉您在遇到异常时进行打印。在一行中添加以打印出异常，以便您获取更多信息。像这样：
} catch (IOException e) {
System.err.println("Couldn't get I/O for the connection to " + hostName);
e.printStackTrace();
System.exit(1);
}
08-18 15:01