这是一个简单的基于客户端/服务器的ping / pong程序。 不幸的是，IT不起作用并显示以下错误消息：
java.net.SocketTimeoutException: Read timed out
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(Unknown Source)
at java.net.SocketInputStream.read(Unknown Source)
at sun.nio.cs.StreamDecoder.readBytes(Unknown Source)
at sun.nio.cs.StreamDecoder.implRead(Unknown Source)
at sun.nio.cs.StreamDecoder.read(Unknown Source)
at java.io.InputStreamReader.read(Unknown Source)
它在CLIENT TASK 30行停止，实际上客户端不读取服务器发送的内容。 代码如下：
package serverClient;
import java.net.*;
import java.io.*;
import java.util.concurrent.*;
public class Server {
public static void main(String[]args){
ExecutorService esp= Executors.newFixedThreadPool(50);
try(ServerSocket ss= new ServerSocket(1027)){
while(true){
try{
Socket s=ss.accept();
Callable<Void> task=new ServerTask(s);
esp.submit(task);
}
catch(BindException be){}
catch(ConnectException ce){}
catch(NoRouteToHostException nrthe){}
catch(IOException ioe){ioe.printStackTrace();}
}
}
catch(Exception e){e.printStackTrace();}
}
}
package serverClient;
import java.util.concurrent.*;
import java.net.*;
import java.io.*;
public class ServerTask implements Callable <Void> {
Socket s;
ServerTask(Socket s){
this.s=s;
}
public Void call(){
BufferedWriter writer=null;
BufferedReader reader=null;
try{
reader=new BufferedReader(new InputStreamReader(s.getInputStream()));
writer=new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
int i=0;
StringBuilder sb=new StringBuilder();
while((i=reader.read())!=-1){
sb.append((char)i);
}
System.out.println("The client sends: "+sb);
writer.write("pong");
writer.flush();
}
catch(IOException ioe){ioe.printStackTrace();}
finally{
try {
writer.close();
}
catch (IOException ioe) {ioe.printStackTrace();}
if(reader!=null){
try{
reader.close();
}
catch(IOException ioe){ioe.printStackTrace();}
}
try{
s.close();
}
catch(IOException ioe){ioe.printStackTrace();}
}
return null;
}
}
package serverClient;
import java.io.IOException;
import java.net.*;
import java.util.concurrent.*;
public class Client {
public static void main(String[] args) {
ExecutorService es= Executors.newSingleThreadExecutor();
try {
Socket s= new Socket(InetAddress.getLocalHost(),1027);
try {
s.setSoTimeout(50000);
}
catch(SocketException se){se.printStackTrace();}
Callable<Void> task=new ClientTask(s);
es.submit(task);
}
catch (UnknownHostException uhe) {uhe.printStackTrace();}
catch (IOException ioe) {ioe.printStackTrace();}
}
}
package serverClient;
import java.util.concurrent.*;
import java.net.*;
import java.io.*;
public class ClientTask implements Callable <Void>{
Socket s;
ClientTask(Socket s){
this.s=s;
}
public Void call(){
BufferedWriter writer=null;
BufferedReader reader=null;
try{
writer=new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
reader=new BufferedReader(new InputStreamReader(s.getInputStream()));
writer.write("ping");
writer.flush();
int i=0;
StringBuilder sb=new StringBuilder();
while((i=reader.read())!=-1){
System.out.println("I'm reading.");
sb.append((char)i);
}
System.out.println("The server sends: "+sb);
}
catch(IOException ioe){ ioe.printStackTrace();}
finally{
try {
writer.close();
}
catch (IOException ioe) {ioe.printStackTrace();}
if(reader!=null){
try{
reader.close();
}
catch(IOException ioe){ioe.printStackTrace();}
}
try{
s.close();
}
catch(IOException ioe){ioe.printStackTrace();}
}
return null;
}
}
答案 0 :(得分：7)
问题在于您在BufferedReader.read()循环中使用while与从连接另一端处理套接字的方式之间的交互。
..read()只会在它正在读取的流结束时返回-1，在这种情况下，这实际上意味着套接字已关闭。在套接字关闭之前，服务器只是阻塞read，等待客户端发送另一个字符。由于服务器在read上阻塞，它将永远不会发送'pong'。客户端正在阻止自己的读取，但最终会达到超时。
TCP套接字用于处理数据流。如果要使用它来发送离散消息，则需要在客户端和服务器之间强制执行协议，以便每个人都知道完整消息何时到达。在这种情况下，客户端和服务器可以就使用终结符来约定，以指定消息是完整的。例如，他们可以同意在每条消息之后发送\n作为终止符。
因此，例如，在您的客户端中，相关代码如下所示：
writer.write("ping");
writer.write('\n');
writer.flush();
int i=0;
StringBuilder sb=new StringBuilder();
while((i=reader.read())!=-1){
char c = (char)i;
if(c == '\n')
break;
sb.append(c);
}
System.out.println("The server sends: "+sb);