List functions of the setsockopt Function

Source: Internet
Author: User

1. If the socket is already in the established State (usually distinguished by the port number and flag ),
Closesocket (usually does not close immediately and goes through the time_wait process) and wants to continue to reuse the socket:
Bool breuseaddr = true;
Setsockopt (S, sol_socket, so_reuseaddr, (const char *) & breuseaddr, sizeof (bool ));
2. If you want to force close a soket that is already in the connection status after you call closesocket
Time_wait process:
Bool bdontlinger = false;
Setsockopt (S, sol_socket, so_dontlinger, (const char *) & bdontlinger, sizeof (bool ));
3. In the send () and Recv () processes, sometimes due to network conditions and other reasons, sending and receiving cannot be performed as expected, but set the sending and receiving time limit:
Int nnettimeout = 1000; // 1 second
// Sending time limit
Setsockopt (socket, sol_s0cket, so_sndtimeo, (char *) & nnettimeout, sizeof (INT ));
// Receiving time limit
Setsockopt (socket, sol_s0cket, so_rcvtimeo, (char *) & nnettimeout, sizeof (INT ));
4. When sending (), the returned bytes are actually sent (synchronized) or the bytes sent to the socket buffer.
(Asynchronous); by default, the system sends and receives data in 8688 bytes (about 8.5 KB) at a time.
When receiving a large amount of data, you can set a socket buffer to avoid the continuous cyclic sending and receiving of send () and Recv:
// Receiving buffer
Int nrecvbuf = 32*1024; // set it to 32 K
Setsockopt (S, sol_socket, so_rcvbuf, (const char *) & nrecvbuf, sizeof (INT ));
// Sending Buffer
Int nsendbuf = 32*1024; // set it to 32 K
Setsockopt (S, sol_socket, so_sndbuf, (const char *) & nsendbuf, sizeof (INT ));
5. If you want to avoid the impact of copying data from the system buffer to the socket buffer when sending data
Program performance:
Int nzero = 0;
Setsockopt (socket, sol_s0cket, so_sndbuf, (char *) & nzero, sizeof (nzero ));
6. Complete the preceding functions in Recv (). By default, the socket buffer content is copied to the system buffer ):
Int nzero = 0;
Setsockopt (socket, sol_s0cket, so_rcvbuf, (char *) & nzero, sizeof (INT ));
7. Generally, when sending a UDP datagram, you want the data sent by the socket to have the broadcast feature:
Bool bbroadcast = true;
Setsockopt (S, sol_socket, so_broadcast, (const char *) & bbroadcast, sizeof (bool ));
8. When the client connects to the server, if the socket in non-blocking mode is in the connect () process
To set the connect () latency until accpet () is called (this function is set only when there is a significant non-blocking process)
Function does not play a major role in blocked function calls)
Bool bconditionalaccept = true;
Setsockopt (S, sol_socket, so_conditional_accept, (const char *) & bconditionalaccept, sizeof (bool ));
9. If closesocket () is called while sending data (sending () is not completed, and data is not sent ),
The general measure is to "calmly close" Shutdown (S, sd_both), but the data is definitely lost. How to set the program to meet specific requirements?
Application requirements (that is, disable the socket after sending the unsent data )?
Struct linger {
U_short l_onoff;
U_short l_linger;
Linger m_slinger;
M_slinger.l_onoff = 1; // (allowed to stay when closesocket () is called, but there is still data not sent)
// If m_slinger.l_onoff = 0, the function is the same as 2;
M_slinger.l_linger = 5; // (the allowable stay time is 5 seconds)
Setsockopt (S, sol_socket, so_linger, (const char *) & m_slinger, sizeof (linger ));
Note: 1. When the latency is set for a non-blocking socket, it is not very useful. It is best not to use it;
2. If you want the program to not experience so_linger, you need to set so_dontlinger, or set l_onoff = 0;
10. A program that is rarely used in SDI or dialog can record the debugging information of socket:
(I tested this function not long ago, and the mode information can be saved, including the parameters during socket creation.
Specific protocols and error code can be recorded)
Bool bdebug = true;
Setsockopt (S, sol_socket, so_debug, (const char *) & bdebug, sizeof (bool ));


In fact, I think 5th entries should be worth noting.
Int nzero = 0;
Setsockopt (socket, sol_s0cket, so_sndbuf, (char *) & nzero, sizeof (nzero ));
I remember some of my friends mentioned that although the socket was successfully sent, it was actually only sent to the data buffer, but it was not actually sent on the physical device. Through this statement, set the sending buffer to 0, that is, after the sending buffer is blocked, once the sending is returned (of course, it is blocked ), it can be confirmed that the data is already being sent ^ _ ^, but this may affect the system performance (this is the problem ^_^)

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