Iranian students clash with riot police during a protest in Tehran on Dec. 30. The government has restricted internet access and online messaging services. (Str/Epa-Efe/Rex/Shutterstock/Str/Epa-Efe/Rex/Shutterstock)

Ben Abdi sent his sister in Iran two messages on Tuesday and by the weekend hadn't heard a peep back.

"How's dad?"

"What's happening?"

He sent the messages over the messaging service WhatsApp, but by Friday evening the checks next to the messages hadn't even switched blue, meaning they were still unread.

Was she okay? Why hadn't she read them? Where was she?

For many Iranians living in exile, the past nine days have been a mix of emotions — fear, foreboding, hope — as they intently watch, as best they can, the deadly unrest unfolding in their native land.

The demonstrations, which began Dec. 28 in Mashhad before rippling quickly and spontaneously across Iran, have resulted in at least 20 deaths and hundreds of arrests. Many of those taking to the streets are young and working-class, rallying against high youth unemployment, rising prices and poor wages.

For some Iranians living in Britain, which has one of the largest diasporas in Europe, it has been a struggle to stay in touch with family and keep abreast of events back home because of restrictions placed on social media tools.

"If you send 10 messages, one will get through," said Abdi, a 45-year-old Iranian who runs a Persian restaurant in north London, festooned with ancient Iranian artifacts and seasonal decorations, including a Christmas tree with a red star. He said his sister's Telegram channel has been worryingly inactive. She's a beautician and normally posts a couple of photos of her clients' hairdos on the Internet messaging service every day. She hasn't posted any for about six days, he said.

Analysts say Iranian authorities have tried to crack down on the unrest by restricting access to the Internet and trying to control social media — sometimes blocking information, sometimes using social media to peddle their own messages.

Sanam Vakil, an Iran expert at Chatham House, a London-based think tank, said the Iranian government has been "really sophisticated in using social media to police society and groups. They very quickly started doing that, sending messages using social media to warn people not to join protests."

She also stressed that the restrictions, including on Internet access in some areas, have been "patchy" rather than a total blackout.

Within days of the protests starting, authorities started restricting some social media tools, including Telegram, which is wildly popular in Iran.

Many Iranians in Britain interviewed for this article said they were still receiving social media messages, including on Telegram, but fewer and less frequently than normal. Several people said they began to have connectivity issues around Tuesday.

"Oh, I just had a reply to a Telegram message — that's the beep you heard," said Shadi, 42, during a phone interview. "I messaged them two hours ago," she said, noting that normally she would have received a reply instantly.

Shadi, who asked that her surname and job title not be used, works for a company that imports heavy machinery into Iran.

Like many Iranians who live overseas, she's eagerly following the unfolding events, watching videos uploaded to her Facebook and Instagram feeds, some of which featured protesters saying the date the video was recorded, so she could tell whether there was a delay.

"It's scary this time," she said, comparing the unrest to protests in 2009 prompted by the outcome of national elections in Iran. She said hearing protesters chant "death to this, death to that" sends "a chill down my spine. To hear people in Iran say it as openly as they are saying it is scary, because this regime is brutal."

As traditional Persian music played in the background at Abdi's restaurant in north London, Iranians were discussing the art of talking about the demonstrations with people inside Iran without mentioning the demonstrations.

Maryam, 37, said she chose to stop using Telegram. "It's too dangerous. It's too controlled," she said. She still communicates daily with her sister in Iran but uses WhatsApp and Tango, she said, and even then, "We are afraid to say something about them, so we say just, 'Hi, how are you?' "

"In any contact from Iran to another country, we assume they are listening to everything," said Nader Shamoo, 46, who added that when it comes to topics like the demonstrations, he talks to his 73-year-old mother in Iran in "coded" language. He did not elaborate.

"Instead of saying, 'Have you seen the protests?' you might say, 'Have you gone out for shopping?' " interjected a man sitting across the table from him, which prompted a slight smile and nod.

When asked whether they are keeping abreast of the latest developments inside Iran, the two men whipped out their smartphones and began scrolling through about a dozen videos of protests on their Facebook and Instagram feeds that had been uploaded Friday evening.

In one video, a bus pulled up and the crowd scattered. "They have come to kill the people," said Shamoo, pointing at the bus, which he believed was transporting security forces.

The Iranian government is like the "mafia," he said, adding that the economic pressures on working-class people were severe. "Iran is a rich country, and yet there is so much pressure on normal people, wages, food, money — everything."

Will the current protests change things?

"We hope so," he said, scrolling through his Facebook feed. "We hope so."