SEND

Use the SEND command to send an outgoing message on the connected socket.

When the socket is a TCP socket, the following conditions apply:

If the socket is in blocking mode and if the total amount of data to be sent cannot be processed by the stack when the command is issued, the command blocks until the data can be sent.
If the socket is in nonblocking mode and if the total amount of data to be written cannot be processed by the stack when the command is issued, the command returns the number of bytes that were successfully written. If none of the data can be written, the command returns the value -1 and the 35 EWOULDBLOCK error message .

When the socket is a connected UDP socket, the SEND command either is completed or failed. A connected UDP socket does not return the 35 EWOULDBLOCK error message .

Guideline: Place the SEND command in a loop to ensure that all the data is written. For a TCP socket, a partial write operation might occur regardless of whether the socket is in blocking or nonblocking mode. A partial write operation occurs when the stack copies some but not all of the application data:

If a partial write operation occurs on a socket in blocking mode, the blocking socket is interrupted. The return value contains the number of bytes written, and the return code contains the reason for the interruption. In such cases, consider ending the connection.
If a partial write operation occurs on a socket in nonblocking mode, the return value indicates the number of bytes that were successfully sent. If this number is less than the number of bytes specified on the SEND command, repeat the SEND command until all data is written. The blocking condition can last for a long time, so use other strategies to ensure that the application does not remain in a busy loop sending data.

Tips:

Use the SELECT command to determine whether a socket is ready to send additional data. To do so, test the socket for a WRITE event.
If the SO_ASCII socket option is enabled, then the data received is translated from EBCDIC to ASCII.

Format


>>-SOCKET--(--"SEND"--,--socketid--,--data--+--------------+--)-><
                                            '-,--sendflags-'

Parameters

socketid

The socket descriptor.

data

The data to be sent.

sendflags

Optional flags that specify how the data is sent. The following flags are supported:

MSG_OOB: Sends the data out-of-band. Out-of-band data is supported only for stream sockets created in the AF_INET domain. The values OOB or OUT_OF_BAND are supported also.
MSG_DONTROUTE: Specifies that the data is routed by the calling program. The value DONTROUTE is supported also.

Returned value

The command returns a string that contains the return code and the amount of data sent, for example, 0 19. The return code can be 0, a REXX socket API error number, or the REXX TCP/IP error number that is set by the socket command. The return code 0 indicates that the requested socket command was completed successfully.

See Socket call error return codes for additional information about the numeric error codes that are returned by this command.

The following REXX TCP/IP error numbers can be returned:

4 EINTR
9 EBADF
5 EIO
22 EINVAL
32 EPIPE
35 EWOULDBLOCK
38 ENOTSOCK
40 EMSGSIZE
45 EOPNOTSUPP
54 ECONNRESET
57 ENOTCONN

The following REXX socket API error numbers can be returned:

2001 EINVALIDRXSOCKETCALL
2005 ESUBTASKNOTACTIVE
2009 ESOCKETNOTDEFINED

LE C/C++ equivalent

int send(int socket, char *buffer, int length, int flags);

Code example

See the EZARXS03 REXX sample in the SBLSCLI0 file for an example of using the SEND command.