Nationwide Conference play-off chasers Accrington Stanley have to do it all again at second division Colchester - but they should have won this third round tie at the first attempt.
Stanley, the only part-timers left in the competition, dominated the second half with keeper Simon Brown denying the Reds in front of a sell-out crowd.
However, Accrington also had the woodwork to thank for saving them as Scott McGleish headed against the crossbar ten minutes from time.
Stanley boss John Coleman said: "It felt like a defeat. We created a handful of chances and their keeper must have been man of the match as he produced some world class saves.
"We had plenty of chances to win it but we will go down to their place and give it our best shot." Colchester manager Phil Parkinson admitted: "I knew it would be tough. Many of the Conference sides are better than the league sides and it is no surprise to me they did so well." Colchester hit the post as early as the tenth minute. Karl Duguid hit a strike from the edge of the area, Stanley keeper James Speare left it but it hit the post before bouncing out to safety.
Stanley's top scorer Paul Mullin had an effort saved by Colchester keeper Simon Brown while Lutel James saw his right-foot shot sail agonisingly wide of the post on 32 minutes.
Rory Prendergast had an effort cleared off the line in the first half while after the break Brown denied sub Steve Flitcroft with a point-blank save from eight yards out.
On 55 minutes James flicked the ball over the keeper but could only watch in agony as his shot hit the crossbar while Brown denied Prendergast on the line.
Just ten minutes from time Colchester's top scorer McGleish had Speare beaten but headed against the bar as the game went from end to end.
Mullin could have written the headlines two minutes from time but headed wide while Brown pulled off a one-handed save in injury time to keep out Paul Cook.