If the Tanzanian passport holders want to apply visa at Vietnam Embassy, they should to know that:
Visa administrative Institution: Vietnam Embassy
Processing time: depends on you how fast you need. But for sure, you should make a call to Vietnam Embassy for details.
Required Documents: passport, money and 1 new envelope with stamp on it and your exact home address in order to avoid losing issues.
How to apply: please take a look at contact information of Vietnam Embassy below
EMBASSY OF VIETNAM IN TANZANIA
Address: Plot 15, Bongoyo Road, Oysterbay, PO Box: 9724 Dar Es Salaam
Phone: (+255) 222664535
Fax: (+255) 222664537