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what is SO_LINGER and TCP_NODELAY?

Posted on 1998-02-16
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Could you tell me what Socket's get/setSoLinger() and get/setTcpNoDelay() mean?
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Question by:luoyue
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jhance earned 40 total points
ID: 1233095
SO_LINGER:

To facilitate this usage, the sockets interface provides for controls by way of the socket option mechanism that allow the programmer to indicate whether the implicit shutdown sequence should be graceful or abortive, and also whether the closesocket function should linger (that is not complete immediately) to allow time for a graceful shutdown sequence to complete. These important distinctions and the ramifications of using closesocket in this manner have not been widely understood.

By establishing appropriate values for the socket options SO_LINGER and SO_DONTLINGER, the following types of behavior can be obtained with the closesocket function:

Abortive shutdown sequence, immediate return from closesocket.


Graceful shutdown, delaying return until either shutdown sequence completes or a specified time interval elapses. If the time interval expires before the graceful shutdown sequence completes, an abortive shutdown sequence occurs, and closesocket returns.


Graceful shutdown, immediate return ¾ allowing the shutdown sequence to complete in the background. Although this is the default behavior, the application has no way of knowing when (or whether) the graceful shutdown sequence actually completes.


TCP_NODELAY:

The TCP_NODELAY option disables the Nagle algorithm. The Nagle algorithm is used to reduce the number of small packets sent by a host by buffering unacknowledged send data until a full-size packet can be sent. However, for some applications this algorithm can impede performance, and TCP_NODELAY can be used to turn it off. Application writers should not set TCP_NODELAY unless the impact of doing so is well-understood and desired, since setting TCP_NODELAY can have a significant negative impact on network performance. TCP_NODELAY is the only supported socket option which uses level IPPROTO_TCP; all other options use level SOL_SOCKET.


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by:luoyue
ID: 1233096
Will you please tell me how to set the parameters in JAVA(not C) to achieve the three functions respectively you mentioned?
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by:jhance
ID: 1233097
On a Socket object (called mySocket) you can do this:

mySocket.setTcpNoDelay(true);
mySocket.setSoLinger(true, 100);


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