6.4.5 N_Data--Data

Synopsis

#include <stream.h>
 #include <netx25/x25_proto.h >

 struct strbuf ctlb;
 struct strbuf datab;

 struct xdataf control;
 char          data[MAX_LENGTH];
 .
 .
 .
 ctlb.len = sizeof(struct xdataf);
 ctlb.buf = (char *)control;

 datab.len = MAX_LENGTH;
 datab.buf = data;

 putmsg(x25_fd, &ctlb, &datab, 0);

Description

N_Data is used to transfer data across the X.25 interface. The synopsis shows a putmsg. Example 6-1 shows how a getmsg can be constructed. The control part of the Data packet is defined by the xdataf structure. The data part of the message contains the user data.

The xdataf structure is shown below:

struct xdataf {
 	unsigned char xl_type; /* Always XL_DAT */
 	unsigned char xl_command; /* Always N_Data */
 	unsigned char More; /* Set when more data is required
                            to complete the nsdu */
 	unsigned char setDbit, /* Set when data carries X.25 D-bit */
 	unsigned char setQbit; /* Set when data carries X.25 Q-bit */
 }; 

The members used by xdataf are.

No acknowledgement for this data is given to, or expected from, the application unless the D-bit is set and application-to-application Receipt Confirmation is being used.