I have a client who wants to create a real state web but with only 1 page and everything should be done dynamically, preferably using websockets. Technically speaking it's possible, but my question is: Is it possible to do it and still have a good page rank? Is there any example os a similar page?
Single page sites can rank. However, the protocol you describe can be used in a way that may confuse search engines. I am not an expert, but this is my thought.
Search engines rank pages. The more pages that rank well the better the site performs overall. It is possible that a single page site can rank rather well. However, there is no denying that content is what search engines are looking for and a site with multiple pages of content tend to perform better than single page sites. This is a given.
Dynamic sites can perform rather well. However, I believe that the key principle is: If search engines see the dynamic content as separate pages then each pseudo page should rank according to CTR from the SERPs and so on. It is not likely that all of these types of pages will receive organic links according to how they are structured and created.
If the site proposed does not appear as a single page, but rather several pages, then you may be okay assuming that these pages can be constructed in a way that allows them to perform well in search engines; that is, good and valid content, proper use of SEO tactics, and popularity of the SERP link just off the top of my head. However, the examples I saw differ from the traditional passing of the parameters in a new HTTP request that we are used to seeing. It must be determined if your use of the more live dynamic would be seen as separate pages or not. Based upon the examples I have seen, I doubt it. But you are likely the best judge.
If search engines see the site as a single page that constantly changes, you may never rank as you can potentially given the constant change. Sites use long-tail search terms as well as trend search-terms to carve out search space for themselves. If your content is a single page that constantly changes, this may be a real challenge that may or may not have an answer.
It appears that websockets are designed for web applications and not for driving ordinary content. Content is what sells a site to Google and users. From what I can see, the use of websockets is not a bad idea from the standpoint of providing data from the back-end as a web application, but would fail the test for ordinary content which should exist for any site to succeed. Dynamic content sites alone often fail though not exclusively. The successful are often mixed with traditional content. I feel that a single page site with this mechanism would not perform well in search. But given the thoughts I have provided, I would devise an experiment to explore whether a search engine would see this as a single page verses multiple pages. From there, you will have your answer.
If it were up to me, the proposed single page site is not one I would pursue. But call me old fashioned.