Sockets
5.2.11t_send() and t_sendto()
These functions are used to transmit a message.
Syntax
int t_send(int s, char *msg, int len, int flags)
int t_sendto(int s, char *msg, int len, int flags,
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struct sockaddr *to) |
where: |
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s |
Is a socket descriptor created with t_socket(). |
msg |
Is a pointer to the data to be sent. |
len |
Is the number of bytes to be sent. |
flags |
Are flags that control how the data is to be sent (see below). |
to |
Is the destination to which the data is to be sent. |
Return value
Returns one of the following:
number |
The number of bytes received, if successful. |
–1 |
If not successful. The internal socket variable errno is set to one of the |
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errors listed in ipport.h. The value of errno can be retrieved by a call |
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to t_errno(socket). |
Usage
You can only use the t_send() function when the socket is in a connected state. The t_sendto() function can be used at any time.
The flags parameter is formed from the bitwise OR of zero or more of the following:
MSG_OOB |
Sends out-of-band data. Only SOCK_STREAM sockets support |
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out-of-band data. |
MSG_DONTROUTE |
The SO_DONTROUTE option is turned on for the duration of the |
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operation. It is used only by diagnostic or routing programs. |
If the socket does not have enough buffer space available to hold the message being sent, the t_send() functions block, unless the socket has been placed in nonblocking input/output mode (see t_setsockopt() on page 5-19).
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Copyright © 1998-2001 ARM Limited. All rights reserved. |
ARM DUI 0144B |
Sockets
5.2.12t_setsockopt()
This function sets the options associated with a socket.
Syntax
int t_setsockopt(long socket, int optname, char *optval)
where:
socket Is the identifier of the socket to be changed.
optname Is the name of the option to be set.
optval Is the value the option will be set to. The parameter should be nonzero to enable a boolean option, or zero if the option is to be disabled. Most socket-level options take an int parameter for optval.
Return value
Returns one of the following:
0 |
If successful. |
–1 |
If not successful. The internal socket variable errno is set to one of the |
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errors listed in ipport.h. The value of errno can be retrieved by a call |
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to t_errno(socket). |
Options
The following options are available:
SO_BIO |
This sets the socket to blocking mode. Operations on the socket |
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are blocked until completion. |
SO_BROADCAST |
This boolean value requests permission to send broadcast |
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datagrams on the socket. Broadcast was a privileged operation in |
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earlier versions of the system. |
SO_CALLBACK |
This registers a callback function for use with the TCP Zero-Copy |
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API. See Chapter 7 The TCP Zero-copy API for more information. |
SO_DONTROUTE |
This boolean value indicates that outgoing messages must bypass |
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the standard routing facilities. Instead, messages are directed to |
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the appropriate network interface according to the network |
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portion of the destination address. |
ARM DUI 0144B |
Copyright © 1998-2001 ARM Limited. All rights reserved. |
5-19 |
Sockets
SO_KEEPALIVE |
This boolean value enables the periodic transmission of messages |
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on a connected socket. If the connected party fails to respond to |
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these messages, the connection is considered broken. |
SO_LINGER |
This option controls the action taken when unsent messages are |
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queued on socket and a t_socketclose() is performed. |
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If the socket promises reliable delivery of data and SO_LINGER is |
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set, the system blocks the process on the t_socketclose() |
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attempt until it is able to transmit the data or until it decides it is |
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unable to deliver the information (a timeout period, termed the |
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linger interval, is specified in the t_setsockopt() call when |
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SO_LINGER is requested). |
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If SO_LINGER is disabled and a t_socketclose() is issued, the |
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system will process the close in a manner that allows the process |
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to continue as quickly as possible. |
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SO_LINGER uses a pointer to a struct linger parameter, |
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defined in socket.h, that specifies the desired state of the option |
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and the linger interval. |
SO_NBIO |
This sets the socket to nonblocking mode. If further operations on |
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the socket cannot complete immediately, they return –1 and set the |
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socket errno variable to EWOULDBLOCK. |
SO_NOBLOCK |
This boolean value enables or disables blocking mode on the |
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socket. If optval is set to zero, the socket is in blocking mode. If |
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optval is set to a nonzero value, the socket is in nonblocking |
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mode. |
SO_OOBINLINE With protocols that support out-of-band data, this boolean option requests that out-of-band data be placed in the normal data input queue as received. It will then be accessible with t_recv().
SO_REUSEADDR This boolean value indicates that the rules used in validating addresses supplied in a t_bind() call must allow reuse of local addresses.
SO_SNDBUF, SO_RCVBUF
These are options to adjust the normal buffer sizes allocated for output and input buffers, respectively. The buffer size can be increased for high-volume connections or can be decreased to limit the possible backlog of incoming data. The system places an absolute limit of 16KB on these values.
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Copyright © 1998-2001 ARM Limited. All rights reserved. |
ARM DUI 0144B |
Sockets
5.2.13t_shutdown()
This function causes all or part of a full duplex connection on the socket associated with socket to be shut down.
Syntax
int t_shutdown(long socket, int how)
where: |
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socket |
Is the connection to be shut down. |
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how |
Is the method of shut down, specified as follows: |
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0 |
Further receives are disallowed |
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1 |
Further sends are disallowed |
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2 |
Further sends and receives are disallowed. |
Return value
Returns one of the following:
0 |
If successful. |
–1 |
If not successful. The internal socket variable, errno, is set to one of the |
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errors listed in ipport.h. The value of errno can be retrieved by a call |
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to t_errno(socket). |
ARM DUI 0144B |
Copyright © 1998-2001 ARM Limited. All rights reserved. |
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