Last Updated: 16/10/12 10:48pm
A fantastic, and unlikely, point for a very happy Michael O'Neill and his players, who put in a Herculean performance to spoil Cristiano Ronaldo's party on his 100th cap. Thanks for tuning in and getting involved over the last couple of hours - hope you enjoyed the match as much as I did! See you again soon.
And it's all over! What a superb point for Northern Ireland against the team ranked third in the world.
Carroll dives over the ball in a comical manner to win a goal kick for Northern Ireland. Surely that's it now?
Portugal give away a needless free-kick on the halfway line as the Green and White army find their voice to cheer their heroes home. Much-needed opportunity to waste a few vital seconds.
Everyone bar Rui Patricio is camped in the Irish half now. But the visitors thump the ball back into Portuguese territory to quell some of the pressure.
Another heart in mouth moment for Northern Ireland as a low cross fizzes across the face of goal. Appears Jonny Evans got a vital touch to stop an almost certain goal.
Five minutes of injury time shown by the fourth official. Can Northern Ireland hold on for a famous point?
Superb shepherding by Hughes who carefully watches Ronaldo perform a flurry of stepovers and does enough to put him off as his low cross only finds Carroll's hands.
Norwood concedes a corner, which Ireland clear as far as Silvestre Varela and the home substitute flashes a fierce shot into the side-netting. Hearts in mouths moment there for the visitors.
Ronaldo surges into the left channel of Northern Ireland's box and cuts back with plenty of team-mates in the penalty area. But it is pulled back too far and the away team escape.
Attack is the best form of defence for Northern Ireland at the moment as Norwood and Corry Evans try to pass their way through a sea of red shirts in the Portuguese half before losing possession.
Aaron Hughes is adjudged by the referee to be taking far too long over a throw-in and goes into his notepad.
Home substitute Silvestre Varela flies into space down the right flank and looks up to see Ronaldo lurking menancingly in the away box. But his cross is far too heavy and sails out for a goal kick.
Still Northern Ireland refuse to give in as McGinn battles bravely to win the ball back on the Portuguese byline. Can they dig deep and stun their hosts for a second time?
The pressure has finally paid off for the Portuguese. But it came in rather fortunate style as a low cross from the left was miskicked by Nani and the ball fell kindly to Postiga, who swivelled to score from close range.
Still Portugal probe, but only have possession around the centre circle as they struggle to break down the determined visitors.
Half a chance for the away team as Rui Patricio careers out of his area to meet a long ball out wide. Niall McGinn beats him there, but is unable to loft the ball over him from a tight angle.
Another wasted opportunity as Veloso can't take the weight off his pass and Northern Ireland win back possession.
A rare, and much-needed, breather for Northern Ireland as Portugal get ready to mount another wave of attacks.
Real end to end stuff as Northern Ireland try to catch their hosts on the counter through Norwood and then Lafferty, either side of another Portugal attack.
CHANCE! Ronaldo races on to a slicing throughball from Pepe and looks to certain to score, before Aaron Hughes rides to the rescue after tracking back with the Portuguese star. Brilliant.
Northern Ireland's workrate has been simply stunning. Every single player is running his guts out, chasing every ball and refusing to allow space for their hosts. But let's not overlook they are playing some wonderful football on the rare occasions they do manage to break too.
Superb pressure by Lafferety as he chases down Rui Patricio to force the home keeper into making mistake and kicking into touch.
Hughes lofts the ball deep into the Portugal box, but no-one in green anticipates as Rui Patricio gathers.
CHANCE! Postiga wastes yet another golden chance as he fails to connect properly with a close-range volley and slices horribly wide. Terrible effort.
Brief respite for the visitors as the referee goes over to his fourth official to talk about a laser pen being pointed at Carroll.
Wave after wave of Portugal attacks here. Carroll punches clear, then blocks low to his right before finally seeing Steven Davis's swipe land on top of his own net. Phew!
Hughes bursts forward before the move breaks down through Lafferty, then Ronaldo looks certain to tap in from close range at the other end. But Northern Ireland breath a huge sigh of relief as it evade the Portuguese skipper.
Pressure from Portugal is beginning to increase as you would expect - be interesting to see how long Northern Ireland can continue this colossal defensive effort before they begin to tire.
CHANCE! Ronaldo gets his first real opportunity when he sweeps Nani's low cross towards goal. But he is denied by Carroll's outstretched left leg. Great instinctive stop.
CHANCE! Postiga finds space to plant a free header straight at Roy Carroll. Turns out he was half a yard offside, but the former Spurs striker should have done better nevertheless.
Ronaldo menancing lets fly from distance but a deflection off an Irish head takes the sting out of it.
Postiga cutely tries to chip into Ronaldo's path inside the away box and, again, it is a poor pass which is far too strong for the Real Madrid superstar.
A rare foray by the visitors as McGinn flies down the left and drills in a cross which Corry Evans, after a lung-bursting run, gets his toe to. Northern Ireland corner....
At the risk of repeating myself here...another poor Portugal cross, this time from Ronaldo, as Carroll brings the ball into his belly.
Pereira sends another right-wing cross intot he box, but it is poor quality and nowhere near a team-mate. Carroll gratefully claims under no pressure.
Ruben Micael fizzes a 25-yard shot over the bar after being allowed too much space. Reckon big Roy Carroll had it covered though.
Nani races on to a long pass and manages to get the ball into the box from the byline. But guess who's there? Yep, that man Jonny Evans to head clear.
Portugal have made a half-time change with Ruben Amorim entering the fray as the home side look to begin a second-half onslaught.
Davy Ryan on Twitter: 'I'm torn!Great to see the underdog puttin up a fight, not helpin my accumulator though!!'
John Mateer: 'Hopefully another famous victory for our Green 'n White army! Will be remembered like our 1-0 over England and 3-2 over Spain!'
A dazed David Magowan has emailed: 'You know it's been a perfect night for Northern Ireland when the great Ronaldo is unsettled....oh yeah and PINCH ME! Is this really happening??'
And that's half-time. So, Northern Ireland fans, your team is half way to a famous, famous victory against Portugal on their own patch. Can you believe what is happening? Tweet me @ J_Jurejko or email email@example.com.
The fourth official shows one minute of injury time before Pereira's long diagonal pass into the box is carefully watched out of play by Carroll.
Ronaldo is fouled and takes a quick free-kick in the away side's half, but Pereira gives away a sloppy pass as McGiven thumps the ball as far downfield as possible.
Carroll confidently strides off his line to gather another hopeful right-wing cross. The Northern Ireland stopper has hardly been stretched by the Portuguese.
Nani whips in another dangerous cross but Jonny Evans, who has been a defensive rock, barges in front of Postiga to head clear.
Lafferty does very well to slow the play down and win Northern Ireland a throw-in deep into Portuguese territory.
A long ball by the visitors finds lone forward Lafferty and relieves some of the intense pressure on their defence.
More danger for the visitors as Carroll comes to claim a Ronaldo cross which skids off the boot of Ryan McGivern at the near post.
Massive let-off there for Cathcart and Northern Ireland as they look to regroup and continue to stifle their illustrious opponents.
WOODWORK! Pereira finds space in the right channel before lofting up a delightful cross which Cathcart swings a boot at to send the ball crashing aginst his own bar.
Ronaldo is furious as Hughes heads past his own post under pressure from Pepe, but the Portuguese do not get the corner.
And Chris Baird nearly makes it two! An audacious long-range effort almost catches out Rui Patricio, who manages to gather and save any further embarrassment.
Can you believe it?! Northern Ireland have only gone and opened the scoring through Niall McGinn. Jonny Evans started the move by striding forward after making a vital interception, before Lafferty slips in McGinn, who calmly clips the ball past Rui Patricio. Sensational.
No chances taken by Roy Carroll, who pushes Nani's looping header from the left byline over his crossbar.
Ruben Micael gives away another needless foul on the halfway line. Can't be far away from a booking - surely?
Northern Ireland sticking stoutly to their game plan of giving no space to the Portuguese. The longer they can keep out their hosts, the more Portugal will get frustrated.
More Portugal pressure, but little quality in the final third from the hosts. Nani balloons a right-wing cross over the penalty area to give possession back to the visitors.
Still the visitors keep possession before the attack breaks down when Ryan McGiven's throw into the Portuguese box is headed clear.
A half chance for Portugal as Pepe rises highest at a home corner to send a thumping header whistling past the post.
Great marauding run by overlapping full-back Aaron Hughes as Northern Ireland again charge forward on the counter. But no-one in green can get a vital touch. Encouraging stuff though.
Stef Galley on Twitter: 'You spoke too soon - it's throwing it down!' Indeed Stef, earlier I promised there would be no rain in Porto, a la Warsaw, but I was proved wrong!
Solid opening 15 minutes from Northern Ireland so far and Michael O'Neill looks happy enough as he chomps on his chewing gum on the sidelines.
Back at the other end, Evans comes to the rescue to superbly head clear another Ronaldo cross at the visitors' near post.
Portugal clear the corner and concede a second as Northern Ireland enjoy a period of pressure. Jonny Evans meets the set-piece but cannot get enough power to test Rui Patricio.
Hughes does enough as Ronaldo's low cross fails to pick out a team-mate, before the away team flood forward on the counter attack to wina corner.
Aaron Hughes, the man tasked with marking Ronaldo, will want to see more of that. But moments later the Portuguese does take control of the ball and launches another runs.
Ah, Ronaldo is human. A long ball picks him out on the flank but his touch evades him and Northern Ireland win a throw-in.
Moutinho tries to pick out Postiga but his lofted pass skips off the turf and Carroll watches the ball out for a goal kick.
Not only do Northern Ireland have to worry about Ronaldo, but there's also the small matter of Nani on the other flank. Thankfully his cross fails to find a red shirt and the visitors clear.
Portugal make another silly mistake with a handball in their own half, but Cathcart cannot get on the end of the Irish free-kick.
Northern Ireland earn a corner as Rui Patricio makes a complete hash of a backpass, and Norwood's curling set-piece is headed away at the far post by a home defender under pressure.
Ronaldo sends a fierce shot wide as he looks to test his former Old Trafford team-mate Roy Carroll early doors.
And Portugal nearly make a breakthrough straight away with a sliding Postiga just inches away from turning in Miguel Lopes's low cross.
Ronaldo receives a huge ovation as a Portuguese FA dignitary makes a presentation to the ex-Manchester United winger to mark his 100th appearance. He's laughing as he sticks a cap onto his head and poses for photos before handing the momento to someone on the sidelines.
Right, here we go. The players have been led out through a bevvy of green-shirted Portuguese beauties and now the national anthems are getting belted out by a bloke who I assume is the home nation's version of Gary Barlow. Only he's less gifted and less good-looking.
The Estadio do Dragao, or Stadium of the Dragons to you and me, is packed to the rafters as the teams line up in the tunnel. There's a pocket of about 1,000 fans in green and white who travelled south and will, I'm sure, be making themselves heard.
Boss Michael O'Neill selects a 4-5-1 formation, leaving out Dean Shiels as Niall McGinn, Corry Evans and Oliver Norwood pack the midfield. Remember, O'Neill is without up to 10 key players, including Gareth McAuley, Shane Ferguson, Chris Brunt and Grant McCann.
All the hype ahead of tonight's match has centred around a certain Cristiano Ronaldo, who wins his 100th cap for the hosts. Only two Portuguese players have achieved this feat - any ideas? It's fastest Tweet first. And no using internet search engines.
N.Ireland: Carroll, McGivern, Cathcart, J Evans, Baird, Davis, K Lafferty, C Evans, McGinn, Norwood, Hughes. Subs: Hodson, Shiels, Healy, Mannus, McCourt, D Lafferty, Grigg, Carson, McGovern.
Portugal: Rui Patricio, Bruno Alves, Pepe, Miguel Veloso, Cristiano Ronaldo, Joao Moutinho, Ruben Micael, Nani, Miguel Lopes, Joao Periera, Helder Postiga. Subs: Eduardo, Custodio, Pizzi, Ruben Amorim, Nelson Oliveira, Sereno, Luis Neto, Silvestre Varela, Eder.
David Johnston (@_David_Johnston) has been in touch on Twitter - and he remains confident Northern Ireland can spring a shock. He says: 'Away form of recent has been poor, but Northern Ireland can surprise as England, Spain and Sweden know. Green and white army!'
Portugal on the other hand have a formidable home record in competitive matches. They have won 21 of their 27 World Cup qualifiers on Portuguese soil.
But they are hardly brimming with confidence having failed to record a win in their past nine games.
Michael O'Neill's men will make history if they win tonight as Northern Ireland have never been victorious in Portugal.
I don't want to evaporate any faint optimism you may have left Northern Ireland fans, but I've got a few statistics which don't make pretty reading...
My name is Jonathan Jurejko and I'll be bringing you all the action from Porto as it happens. And you'll be pleased to know that, unlike Warsaw, there isn't a rain cloud in sight. So it's all systems go with around 40 minutes until kick-off. In the meantime, why don't you get in touch? Can Northern Ireland succeed in near-Mission Impossible? Tell me on Twitter @J_Jurejko, or email firstname.lastname@example.org.