The correct expression is "How are things going at your end?", or just "how are things at your end?". It is simply asking how a person is, when the person is away from the speaker - either talking on the phone, or over the internet. 'At your end' means 'where you are'. You would use this the same way you would use 'how are things?' or simply 'how are you?'. However, only use it when the speaker is actually away from you - on the phone, or over the internet, as I said. It wouldn't be appropriate to ask this when you are face-to-face with someone.