send()--Send Data

Syntax #include <sys/types.h> #include <sys/socket.h> int send(int socket_descriptor, char *buffer, int buffer_length, int flags) Threadsafe: Yes

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

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_OOB

Send data as out-of-band data. Valid only for sockets with an address family of AF_INET and type SOCK_STREAM.

MSG_DONTROUTE

Bypass routing. Valid only for sockets with address family of AF_NS or AF_INET. It is ignored for other address families.

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.

[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

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

1. send() only works with sockets on which a connect() has been issued, since it does not allow the caller to specify a destination address.

2. To broadcast on an AF_INET socket, the socket option SO_BROADCAST must be set (with a setsockopt()).

3. 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()).

Related Information

• fcntl()--Retrieve or Change Descriptor Attributes

• ioctl()--Change Descriptor Attributes

• sendto()--Send Data

• sendmsg()--Send Data or Descriptors or Both

• write()--Write to Descriptor

• writev()--Write to Descriptor Using Multiple Buffers