sendto()--Send Data

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

 int sendto(int socket_descriptor,
            char *buffer,
            int buffer_length,
            int flags,
            struct sockaddr *destination_address,
            int address_length)

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

 ssize_t sendto(int socket_descriptor,
            const void *buffer,
            size_t buffer_length,
            int flags,
            const struct sockaddr *destination_address,
            socklen_t address_length)

The sendto() function is used to send data through a connected or unconnected 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 one or more of 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.

destination_address

(Input) A pointer to a buffer of type struct sockaddr that contains the destination address to which the data is to be sent. The structure sockaddr is defined in <sys/socket.h>.

The BSD 4.3 structure is:

      struct sockaddr {
         u_short sa_family;
         char    sa_data[14];
      };

The BSD 4.4/UNIX 98 compatible structure is:

      typedef uchar   sa_family_t;

      struct sockaddr {
         uint8_t     sa_len;
         sa_family_t sa_family;
         char        sa_data[14];
      };

The BSD 4.4 sa_len field is the length of the address. The sa_family field identifies the address family to which the address belongs, and sa_data is the address whose format is dependent on the address family.

address_length

(Input) The length of the destination_address.

Authorities

When the address family of the socket identified by the socket_descriptor is AF_INET and is running IP over SNA, the thread must have retrieve, insert, delete, and update authority to the APPC device. When the thread does not have this level of authority, an errno of EACCES is returned.

Return Value

sendto() returns an integer. Possible values are:

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

Error Conditions

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

Error Messages

Usage Notes

1. A destination address cannot be specified if the socket pointed to by the socket_descriptor parameter already has a destination address associated with it. To not specify an address, users must set the destination_address field to NULL or set the address_length field to zero. (Not specifying an address by setting the address_length field to zero is an IBM^® extension.)

   Note: The destination_address and address_length fields are ignored if the socket is using a connection-oriented transport service.

2. If the socket is using a connectionless transport device, the socket is not bound to an address, and the socket type is SOCK_DGRAM, the system automatically selects an address (INADDR_ANY or in6addr_any and an available port number) and binds it to the socket before sending the data. The IPV6_ADDR_PREFERECES socket option flags set on setsockopt() will be taken into consideration when selecting the source address on which to send the outgoing data.
   
   
3. To broadcast on an AF_INET socket, the socket option SO_BROADCAST must be set (with a setsockopt()).
   
   
4. 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()).

5. If the socket is using an address family of AF_UNIX, the destination address (which is a path name) is assumed to be in the default coded character set identifier (CCSID) currently in effect for the job. For AF_UNIX_CCSID, the destination address is assumed to be in the format and coded character set identifier (CCSID) specified in the sockaddr_unc.
   
   
6. 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 sendto() API is mapped to qso_sendto98().

Related Information

• _XOPEN_SOURCE--Using _XOPEN_SOURCE for the UNIX 98 compatible interface
  
  
• fcntl()--Perform File Control Command
  
  
• ioctl()--Perform I/O Control Request
  
  
• send()--Send Data
  
  
• sendmsg()--Send Data or Descriptors or Both

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