I'm a Sri Lanka in Hanoi for a training programme, can I take China visa from Hanoi?

Dear Respectable Sir,

Am a Government officer in Sri Lanka and coming to Hanoi, Viet nam for a training programme on first week of October… I would like to express my interest to visit China on this way for few days on my vacation.. Please, Let I know that can I take Visa from Hanoi, can I travel by train and how far from Hanoi to china. ..I shall be greatly appreciated if you could provide the information.

Sincerely,

R. Kumudini