On every project, in how many days project meeting is required? and who are the key people required in those meetings?

What you want to know is called " Communication Matrix " which is an integral part of Communication & Stakeholder Management Plan .

Type of communication and the frequency of communication varies from project to project depending on the project stakeholders and their project communication requirements. But generally speaking , Project Team meetings involving project team is done ONCE in a week to review the status of the project with the team and Project Status Report meeting involving Project Sponsor , Project Stakeholders , PMO & Project Team is done either Monthly or Weekly . Both the meetings are conducted by Project Manager. 

Apart from the above main meetings , there are other meetings such as Design / Technical , Scope Variance analysis meeting , Escalation process meetings etc. involving different stakeholders at different timings.

All team members meet 1 x a week to see what progress has been made and the milestones being met.

It does not matter if it is one or several projects which is handled by the same team. 

The more projects and different teams the more meetings.

According to communication plan but generally meeting is held once a week with client to discuss  the work progress

Thanks for the invitation. I second the answer given by Mr. Krishna Khasanis.

for the project meeting P.M , site engineer QC and supervisor are the key people.

project meeting is depends on site condition, schedule and the work progress.

il faut faire des reunion chaque semain pour voir les avancements, les problemes rencontrees, proposer  des solutions, evaluer le travail de la semaine. ca c'est entre l'équipe de travail (l'ensemble des chefs d'équipes avec le responsable du projet).

mais avec les parties externes du projet, la réunion aura lieu le temps qui'il faut, soit pour résoudre ou assainer une situation, ou bien pour presenter le travail executee

Meeting with project sponsor to kick off the project. Then Scrum meeting weekly.

Meeting depends upon the nature of projects. Each project must have work scope a mutually agreed documents between client and vendor. Set goals for the projects and form a steering committee share members from vendor and client. Form a project progress monitoring committee which look after day to day progress. The steering committee will look after goals progress mentioned in scope documents. Project progress monitoring meeting could be held on every week.  

Thank you. I agree with Mr. Krishna KHASANIS.

Thank you for your invitation

Each greeting for all the interest and useful answers

Thanks 

Good answer which given by Mr. Kreshna, i support him