send()--Send Data

BSD 4.3 Syntax

  #include <sys/types.h>
  #include <sys/socket.h>

 int send(int socket_descriptor,
          char *buffer,
          int buffer_length,
          int flags)

  Service Program Name: QSOSRV1

  Default Public Authority: *USE

  Threadsafe: Yes

UNIX^® 98 Compatible Syntax

  #define _XOPEN_SOURCE 520
  #include <sys/socket.h>

 ssize_t send(int socket_descriptor,
          const void *buffer,
          size_t buffer_length,
          int flags)

  Service Program Name: QSOSRV1

  Default Public Authority: *USE

  Threadsafe: Yes

The send() function is used to send data through a connected socket.

There are two versions of the API, as shown above. The base IBM^® i API uses BSD 4.3 structures and syntax. The other uses syntax and structures compatible with the UNIX 98 programming interface specifications. You can select the UNIX 98 compatible interface with the _XOPEN_SOURCE macro.

Parameters

socket_descriptor

(Input) The socket descriptor that is to be written to.

buffer

(Input) The pointer to the buffer in which the data that is to be written is stored.

buffer_length

(Input) The length of the buffer.

flags

(Input) A flag value that controls the transmission of the data. The flags value is either zero, or is obtained by performing an OR operation on the following constants:

`MSG_EOR`	Terminate a record, if supported by the protocol.
`MSG_OOB`	Send data as out-of-band data. Valid only for sockets with an address family of `AF_INET` or `AF_INET6` and type `SOCK_STREAM`.
`MSG_DONTROUTE`	Bypass routing. Valid only for sockets with address family of `AF_INET`. It is ignored for other address families.

Authorities

No authorization is required.

Return Value

send() returns an integer. Possible values are:

-1 (unsuccessful)
n (successful), where n is the number of bytes sent.

Error Conditions

When send() fails, errno can be set to one of the following:

[EACCES]	Permission denied. This error code indicates one of the following: Destination address specified a broadcast address and the socket option `SO_BROADCAST` was not set (with a setsockopt()). The process does not have the appropriate privileges to the destination address. This error code can only be returned on a socket with a type of `SOCK_DGRAM` and an address family of `AF_INET`.
[EBADF]	Descriptor not valid.
[ECONNREFUSED]	The destination socket refused an attempted connect operation. This error code can only be returned on sockets that use a connectionless transport service.
[EDESTADDRREQ]	Operation requires destination address. A destination address has not been associated with the socket pointed to by the socket_descriptor parameter. This error code can only be returned on sockets that use a connectionless transport service.
[EFAULT]	Bad address. The system detected an address which was not valid while attempting to access the buffer parameter.
[EHOSTDOWN]	A remote host is not available. This error code can only be returned on sockets that use a connectionless transport service.
[EHOSTUNREACH]	A route to the remote host is not available. This error code can only be returned on sockets that use a connectionless transport service.
[EINTR]	Interrupted function call.
[EINVAL]	Parameter not valid. The buffer_length parameter specifies a negative value.
[EIO]	Input/output error.
[EMSGSIZE]	Message size out of range. The data to be sent could not be sent atomically because the size specified by buffer_length is too large.
[ENETDOWN]	The network is not currently available. This error code can only be returned on sockets that use a connectionless transport service.
[ENETUNREACH]	Cannot reach the destination network. This error code can only be returned on sockets that use a connectionless transport service.
[ENOBUFS]	There is not enough buffer space for the requested operation.
[ENOTCONN]	Requested operation requires a connection. This error code can only be returned on sockets that use a connection-oriented transport service.
[ENOTSOCK]	The specified descriptor does not reference a socket.
[EOPNOTSUPP]	Operation not supported. This error code indicates one of the following: The flags parameter specifies a value that includes the `MSG_OOB` flag, but the socket_descriptor parameter points to a connectionless socket. The flags parameter specifies a value that includes the `MSG_OOB` flag, but the socket_descriptor parameter points to a socket that does not have an address family of `AF_INET` or `AF_INET6`.
[EPIPE]	Broken pipe.
[EUNATCH]	The protocol required to support the specified address family is not available at this time.
[EUNKNOWN]	Unknown system state.
[EWOULDBLOCK]	Operation would have caused the thread to be suspended.

Error Messages

Message ID	Error Message Text
CPE3418 E	Possible APAR condition or hardware failure.
CPF9872 E	Program or service program &1 in library &2 ended. Reason code &3.
CPFA081 E	Unable to set return value or error code.

Usage Notes

send() only works with sockets on which a connect() has been issued, since it does not allow the caller to specify a destination address.
To broadcast on an AF_INET socket, the socket option SO_BROADCAST must be set (with a setsockopt()).
When using a connection-oriented transport service, all errors except [EUNATCH] and [EUNKNOWN] are mapped to [EPIPE] on an output operation when either of the following occurs:
- A connection that is in progress is unsuccessful.
- An established connection is broken.
To get the actual error, use getsockopt() with the SO_ERROR option, or perform an input operation (for example, read()).
When you develop in C-based languages and an application is compiled with the _XOPEN_SOURCE macro defined to the value 520 or greater, the send() API is mapped to qso_send98().

Related Information

_XOPEN_SOURCE--Using _XOPEN_SOURCE for the UNIX 98 compatible interface
fcntl()--Perform File Control Command
ioctl()--Perform I/O Control Request
sendto()--Send Data
sendmsg()--Send Data or Descriptors or Both
write()--Write to Descriptor
writev()--Write to Descriptor Using Multiple Buffers

API introduced: V3R1

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