nng_msg_append - append to message body

       The nng_msg_append() family of functions appends data to the end of the body of message msg, reallocating
       it if necessary. The first function appends size bytes, copying them from val. The remaining functions
       append the value specified (such as val32) in network-byte order (big-endian).

       NNG_ENOMEM
           Insufficient free memory exists.

       nng_msg_append - append to message body

       These functions return 0 on success, and non-zero otherwise.

nng_msg_alloc(3), nng_msg_body(3), nng_msg_chop(3), nng_msg_free(3), nng_msg_insert(3), nng_msg_len(3),
       nng_msg_realloc(3), nng_msg_trim(3), nng_strerror(3), nng_msg(5), nng(7)

                                                   2025-04-20                                  NNG_MSG_APPEND(3)

           #include <nng/nng.h>

           int nng_msg_append(nng_msg *msg, const void *val, size_t size);
           int nng_msg_append_u16(nng_msg *msg, uint16_t val16);
           int nng_msg_append_u32(nng_msg *msg, uint32_t val32);
           int nng_msg_append_u64(nng_msg *msg, uint64_t val64);