Application of Java NiO in Network Programming

In fact, Java NiO introduces an asynchronous mechanism. asynchronous I/O has select poll epoll in Linux and supports multiplexing. In Java, it is implemented through a complete set of NiO classes, mainly including:

Bytebuffer

Socketchannel

Serversocketchannel

Selector

Selectionkey

 

Registration:

Channel calls register to register with selector,

Remove:

Selectionkey. Cancel // only remove the channel corresponding to the selectionkey from the selector. The socket is still active and needs to be disabled manually.

Channel. Close () // remove from selector, and close the socket object associated with the channel.

 

 

// Obtain a selector

Selector select = selector. open ();

Serversocketchannel Ss = serversocketchannel. open ();

// It must be set to non-blocking.

SS. configureblocking (false );

// Bind to an address

SS. socket (). BIND (New inetsocketaddress ("0.0.0.0", 5858 ));

 

// Register the channel with selector. A selectionkey is associated with the channel.

// When a connection comes in, select can return selectedkeys

SS. Register (select, selectionkey. op_accept );

 

 

 

While (select. Select ()> = 0 ){

// Return the ready keys.

Set <selectionkey> keyready = select. selectedkeys ();

 

// Poll the key in every ready state. The channel can be obtained through the key or deleted from the selector through the key.

For (iterator <selectionkey> iter = keyready. iterator (); ITER. hasnext ();){

Selectionkey Sk = ITER. Next ();

ITER. Remove ();

 

System. Out. println ("cancel" + select. Keys (). Size ());

 

Socketchannel client = NULL;

If (SK. Channel () instanceof serversocketchannel ){

Ss = (serversocketchannel) SK. Channel ();

Client = ss. Accept ();

System. Out. println ("accept:" + client. socket ());

// Client. socket (). Close ();

// It must be set to non-blocking.

Client. configureblocking (false );

// Register non-passive socket to Selector

Client. Register (select, selectionkey. op_read );

}

Else if (SK. Channel () instanceof socketchannel ){

Socketchannel CH = (socketchannel) SK. Channel ();

Bytebuffer recvbuf = bytebuffer. Allocate (100 );

// Bytebuffer in NIO must be used; otherwise, an error occurs.

Int Len = CH. Read (recvbuf );

If (LEN <0 ){

// You must disable the socket before removing it. Otherwise, many sockets are open.

Ch. socket (). Close ();

// Remove the channel from Selector

SK. Cancel ();

Continue;

}

Recvbuf. Flip ();

Ch. Write (recvbuf );

// SK. Cancel ();

System. Out. println ("cancel" + select. Keys (). Size () + "len" + Len );

 

Len = CH. Read (recvbuf );

 

// Disable the channel. At this time, the socket corresponding to the channel is closed and the channel is removed from the selector.

// Ch. Close ();

System. Out. println ("len" + Len );

 

}

Else {

System. Out. println ("error change ");

}

}

}

 

System. Out. println ("End ==== ");