关于使用localhost以外的主机时，我对Java中的SocketServer和Socket连接有疑问。
我正在尝试编写一个简单的聊天程序，希望与我家中的其他人建立联系。这是我创建服务器套接字和套接字的代码：
private static boolean clientIsConnected = false;
public static void main(String[] args) {
new Thread(new Runnable(){
public void run(){
Server server = null;
try{
server = new Server();
clientIsConnected = server.getClient().isConnected();
while(clientIsConnected){
System.out.println("Message From Client: ");
System.out.print(server.recieveMessage());
System.out.println();
}
}catch(IOException e){
e.printStackTrace();
}
finally{
try{
if(server!=null)server.getServer().close();
if(server!=null)server.getClient().close();
}catch(IOException e){
e.printStackTrace();
}
}
}
}).start();
new Thread(new Runnable(){
public void run(){
Client client = null;
try{
Thread.sleep(2000);
client = new Client();
clientIsConnected = client.getClient().isConnected();
System.out.println("Exit with \'!\'");
while(clientIsConnected){
Scanner userInput = new Scanner(System.in);
String message = userInput.next();
clientIsConnected = message.equals("!");
client.sendMessage(message);
}
} catch(InterruptedException i){
i.printStackTrace();
}
catch(IOException e){
e.printStackTrace();
}
finally{
try{
if(client!=null)client.getClient().close();
}catch(IOException e){
e.printStackTrace();
}
}
}
}).start();
}
static class Server{
protected static final int PORT = 50211;
private final ServerSocket server;
protected Socket client;
Server() throws IOException{
server = new ServerSocket(PORT);
client = server.accept();
}
public boolean sendMessage(String message) throws IOException{
if(message == null)return false;
if(message.isEmpty())return false;
client.getOutputStream().write(message.getBytes());
return true;
}
public String recieveMessage() throws IOException{
StringBuilder message = new StringBuilder();
int character;
while((character = client.getInputStream().read())!= -1)
message.append((char)character);
return message.toString();
}
public ServerSocket getServer() {
return server;
}
public Socket getClient() {
return client;
}
}
static class Client extends Server{
Client() throws IOException{
client = new Socket("localhost",PORT);
}
}
ServerRelay（运行）： 运行：
java.net.BindException: Address already in use: JVM_Bind
at java.net.DualStackPlainSocketImpl.bind0(Native Method)
at java.net.DualStackPlainSocketImpl.socketBind(DualStackPlainSocketImpl.java:106)
at java.net.AbstractPlainSocketImpl.bind(AbstractPlainSocketImpl.java:387)
at java.net.PlainSocketImpl.bind(PlainSocketImpl.java:190)
at java.net.ServerSocket.bind(ServerSocket.java:375)
at java.net.ServerSocket.<init>(ServerSocket.java:237)
at java.net.ServerSocket.<init>(ServerSocket.java:128)
at socketrelay.SocketRelay$Server.<init>(SocketRelay.java:100)
at socketrelay.SocketRelay$1.run(SocketRelay.java:28)
at java.lang.Thread.run(Thread.java:748)
java.net.BindException: Address already in use: JVM_Bind
at java.net.DualStackPlainSocketImpl.bind0(Native Method)
at java.net.DualStackPlainSocketImpl.socketBind(DualStackPlainSocketImpl.java:106)
at java.net.AbstractPlainSocketImpl.bind(AbstractPlainSocketImpl.java:387)
at java.net.PlainSocketImpl.bind(PlainSocketImpl.java:190)
at java.net.ServerSocket.bind(ServerSocket.java:375)
at java.net.ServerSocket.<init>(ServerSocket.java:237)
at java.net.ServerSocket.<init>(ServerSocket.java:128)
at socketrelay.SocketRelay$Server.<init>(SocketRelay.java:100)
at socketrelay.SocketRelay$Client.<init>(SocketRelay.java:132)
at socketrelay.SocketRelay$2.run(SocketRelay.java:60)
at java.lang.Thread.run(Thread.java:748)
成功完成（总时间：2秒）
//解决了此问题
static class Client extends Server{
private Socket client;
Client() throws IOException{
client = new Socket("localhost",PORT);
}
@Override
public Socket getClient() {
return client;
}
@Override
public boolean sendMessage(String message) throws IOException{
if(message == null)return false;
client.getOutputStream().write(message.getBytes());
return true;
}
@Override
void close() {
try
{
if(client!=null)client.close();
}
catch(IOException e)
{
e.printStackTrace();
}
}
}
static class Server{
protected static final int PORT = 65535 - new Random().nextInt(300);
ServerSocket server;
Socket serverClient;
public boolean sendMessage(String message) throws IOException{
if(message == null)return false;
serverClient.getOutputStream().write(message.getBytes());
return true;
}
public String recieveMessage() throws IOException{
StringBuilder message = new StringBuilder();
int character;
while((character = serverClient.getInputStream().read())!= -1)
message.append((char)character);
return message.toString();
}
public ServerSocket getServer() {
return server;
}
public void setServer(ServerSocket server) {
this.server = server;
}
public Socket getClient() {
return serverClient;
}
private void setClient(Socket socket) {
serverClient = socket; //To change body of generated methods, choose Tools | Templates.
}
void close()
{
try
{
if(server!=null)server.close();
if(serverClient!=null)serverClient.close();
}
catch(IOException e)
{
e.printStackTrace();
}
}
}
private static volatile boolean didUserExit = false;
public static void main(String[] args) {
startServer();
startClient();
}
static void startClient(){
new Thread(new Runnable(){
public void run(){
Client client = null;
try{
client = new Client();
didUserExit = false;
System.out.println("Exit with \'!\'");
while(!didUserExit){
System.out.println("Send a message to server: ");
Scanner userInput = new Scanner(System.in);
String message = userInput.next();
didUserExit = message.equals("!");
if(!didUserExit)client.sendMessage(message);
}
}
catch(IOException e){
e.printStackTrace();
}
finally{
if(client!=null)client.close();
}
}
}).start();
}
static void startServer(){
new Thread(new Runnable(){
public void run(){
Server server = null;
try{
server = new Server();
while(!didUserExit){
if(server.getServer()== null){
server.setServer(new ServerSocket(server.PORT));
server.setClient(server.getServer().accept());
}
String clientMessage = server.recieveMessage();
if(!clientMessage.isEmpty()){
System.out.println("Message From Client: ");
System.out.print(clientMessage);
System.out.println();
}
}
}catch(IOException e){
e.printStackTrace();
}
finally{
if(server!=null)server.close();
}
}
}).start();
}
现在的问题是这样的：
run:
Exit with '!'
Send a message to server:
Hello world
Send a message to server:
!
Message From Client:
Hello
BUILD SUCCESSFUL (total time: 8 seconds)
请注意发送到服务器的消息如何不包含它必须是的“世界”（“ Hello world”）；第一个空格字符之后的所有内容都将不包括在内。
可能是什么原因引起的...我试图弄清楚这一点，但没有成功。