请问 socket挂死

求助 请教 socket挂死
我写了两个线程对同一个socket进行读写,但是读的操作一直不返回，读方法和写方法加了同步关键字，读的不返回导致写的线程一直BLOCKED，不知道是怎么回事儿，线程堆栈入下，请教高手们指点一下：

读的堆栈如下：
        java.net.SocketInputStream.socketRead0(Native Method)                                             
        java.net.SocketInputStream.read(SocketInputStream.java:146)                                             
        java.io.DataInputStream.read(DataInputStream.java:149)                                             
        java.io.ObjectInputStream$PeekInputStream.read(ObjectInputStream.java:2282)                                             
        java.io.ObjectInputStream$PeekInputStream.readFully(ObjectInputStream.java:2295)                                            
 
        java.io.ObjectInputStream$BlockDataInputStream.readUTFBody(ObjectInputStream.java:3035)                                     
        
        java.io.ObjectInputStream$BlockDataInputStream.readUTF(ObjectInputStream.java:2836)                                         
    
        java.io.ObjectInputStream.readString(ObjectInputStream.java:1616)                                             
        java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1337)                                             
        java.io.ObjectInputStream.readObject(ObjectInputStream.java:368)                                             
        java.util.HashMap.readObject(HashMap.java:1046)                                             
        sun.reflect.GeneratedMethodAccessor6.invoke(Unknown Source)                                             
        sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)                                       
      
        java.lang.reflect.Method.invoke(Method.java:616)                                             
        java.io.ObjectStreamClass.invokeReadObject(ObjectStreamClass.java:991)                                             
        java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1865)