Ok, so first of all, it depends on what you consider sleeping through the night. A breastfed baby is considered to sleep through the night at 5 hours. And many believe that as long as the baby isn't waking to play and only for food and going straight back to sleep that they have slept through the night. But I'll assume you're hoping for 10-14 hours of uninterrupted sleep.
My first son slept through the night without waking around 6.5 months old. Once he did, he never went back to not sleeping through the night unless he was sick and then for a short time after his little brother was born.
My second son slept 4-5 hours at a time for one wonderful week when he was about 3 months old, then he cut his first tooth at 3.5 months and was up every 1.5-2 hours until he was 9 months old:( After that, he was up twice a night for another 3 or 4 weeks, and then once a night until after a year old. He went through the whole night sometime after his first birthday and never went back to waking.
I don't believe in forcing a baby to sleep through the night before they are ready. My kids both slept 12-14 hours when they were ready. I responded to their cries until they didn't need me to:) It's such a short time in your life. don't rush it, don't push it. Just enjoy being needed, too soon you'll be pushed away.