linux上TCP connection timeout问题解决办法

java.net.SocketTimeoutException: connect timed out 
客户端异常:connect timed out 
  at java.net.PlainSocketImpl.socketConnect(Native Method) 
  at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:345) 
  at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) 
  at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) 
  at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) 
  at java.net.Socket.connect(Socket.java:589) 

while (1) { 
        jlong newTime; 
#ifndef USE_SELECT 
        { 
          struct pollfd pfd; 
          pfd.fd = fd; 
          pfd.events = POLLOUT; 
 
          errno = 0; 
          connect_rv = NET_Poll(&pfd, 1, timeout); 
        } 
#else 
        { 
          fd_set wr, ex; 
          struct timeval t; 
 
          t.tv_sec = timeout / 1000; 
          t.tv_usec = (timeout % 1000) * 1000; 
 
          FD_ZERO(&wr); 
          FD_SET(fd, &wr); 
          FD_ZERO(&ex); 
          FD_SET(fd, &ex); 
 
          errno = 0; 
          connect_rv = NET_Select(fd+1, 0, &wr, &ex, &t); 
        } 
#endif 
 
        if (connect_rv >= 0) { 
          break; 
        } 
        if (errno != EINTR) { 
          break; 
        } 
 
        /* 
         * The poll was interrupted so adjust timeout and 
         * restart 
         */ 
        newTime = JVM_CurrentTimeMillis(env, 0); 
        timeout -= (newTime - prevTime); 
        if (timeout <= 0) { 
          connect_rv = 0; 
          break; 
        } 
        prevTime = newTime; 
 
      } /* while */ 
 
      if (connect_rv == 0) { 
        JNU_ThrowByName(env, JNU_JAVANETPKG "SocketTimeoutException", 
              "connect timed out"); 
 
        /* 
         * Timeout out but connection may still be established. 
         * At the high level it should be closed immediately but 
         * just in case we make the socket blocking again and 
         * shutdown input & output. 
         */ 
        SET_BLOCKING(fd); 
        JVM_SocketShutdown(fd, 2); 
        return; 
      } 

newTime = JVM_CurrentTimeMillis(env, 0); 
        timeout -= (newTime - prevTime); 
        if (timeout <= 0) { 
          connect_rv = 0; 
          break; 
        }