客戶端關閉，伺服器端SocketException異常解決方案
已親測(伺服器端不完整，關鍵處已寫，請模擬者自行補充)。（伺服器端與客戶端程式碼都是用執行緒）
解析：通過R，伺服器端判斷客戶端是來請求連結還是做其他事情。
當客戶端傳送R+ 使用者名稱時 伺服器端會對使用者名稱進行儲存，然後給客戶端傳送連線成功訊息。
當客戶端傳送R+關閉時。伺服器端知曉客戶端已關閉，然後斷開怎麼迴圈，刪除掉儲存的伺服器名字。
客戶端：public class ClientProgram {
BackShowFrame bsf;
Socket socket;
public ClientProgram(String name){//獲取客戶端名字。
conserver(name);
}
public void conserver(String username){//與伺服器建立連線
try {
socket = new Socket("localhost",5300);
new ReceiveThread().start();
write("R,"+username);
} catch (Exception e) {
System.out.println("連線失敗");
}
}
public void write(String msg){//傳送訊息
try {
OutputStream os = socket.getOutputStream();
os.write(msg.getBytes());
os.flush();
} catch (IOException e) {
e.printStackTrace();
}
}
private String usename;
public String getUsename(){
return usename;
}
public void setUsename(String usename){
this.usename = usename;
}
boolean isOnline = true;
class ReceiveThread extends Thread{//讀取訊息執行緒
public void run(){
try {
InputStream inputstream = socket.getInputStream();
byte[] buffer = new byte[1024];
while(isOnline){
int n = inputstream.read(buffer);
String receiver = new String(buffer,0,n);
if(receiver.startsWith("R")){
System.out.println("連線成功");
}
if(receiver.startsWith("M")){
System.out.println(receiver);
String[] msg = receiver.split(",");
System.out.println(msg[2]);
String send = msg[3];
if(!(send.equals("後臺"))){
setUsename(send);
}
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
InputStream inputStream = socket.getInputStream();//接受伺服器訊息
byte[] buffer = new byte[1024];
while(clientOnline){
int n = inputStream.read(buffer);
String s = new String(buffer,0,n);
System.out.println(s);
String[] temp = s.split(",");
String name = temp[1];
if(s.startsWith("R")){
if(!(temp[1].equals("關閉"))){
OutputStream os = socket.getOutputStream();
os.write(("R,"+"連線成功").getBytes());//給使用者傳送連線成功
os.flush();
}else{
clientOnline = false;//當clientOnline = false;時整個執行緒會跳出去，表示對此名字的客戶端監聽結束
}