libssh2_poll_channel_read man page
libssh2_poll_channel_read — check if data is available
int libssh2_poll_channel_read(LIBSSH2_CHANNEL *channel, int extended);
This function is deprecated. Do note use.
libssh2_poll_channel_read(3) checks to see if data is available in the channel's read buffer. No attempt is made with this method to see if packets are available to be processed. For full polling support, use libssh2_poll(3).
Returns 1 when data is available and 0 otherwise.