Create Instant messaging app like whatsapp or youtube?

I love chatting and sharing photos and videos with my friends on social media, but lately I'm thinking a lot about creating my very own Instant messaging app. So, how does one go about doing it?

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if (strstr (s, "niggers") || strstr (s, "kikes") || strstr (s, "gen.lib.rus.ec"))
/* drop connection */;