Next and previous link in custom post type in the same taxonomy term

I have a custom post type name->('portfolio'), with a taxonomy name 'portfolio_category'.

What I want is to add next and previous links on its single page file which is single-portfolio.php. When I click either of the links, it should redirect to the next or previous post in the same post type and in the same taxonomy term.

I used next_post_link() and previous_post_link() but it seems that it only works in single post but not in single custom post type..

Any suggestions will greatly be appreciated.

previous_post_link() and next_post_link() work perfectly with custom post types. You need to paste this code in your single-customposttype.php (which in your case is single-portfolio.php):

<div class="previous-post-link">
                <?php previous_post_link('%link', '<< Previous Post', $in_same_term = true, $excluded_terms="", $taxonomy = 'the-custom-taxonomy-associated-with-your-custom-post-type'); ?>                    
            </div>

            <div class="next-post-link">
                <?php next_post_link('%link', 'Next Post >>', $in_same_term = true, $excluded_terms="", $taxonomy = 'the-custom-taxonomy-associated-with-your-custom-post-type'); ?>                    
            </div>