Nearly 30,000 refugees have entered Croatia since Wednesday — many of whom are hungry, tired and in need of medical aid. Volunteers are working night and day to help, but the people waiting at various refugee centers and train stations, trying to find a way into western Europe, are desperate for information. They are trying to figure out routes to get to Germany, and with the borders to Slovenia and Hungary closing and reopening every few hours, that information is vital.

And without Internet access, they have none.

A group based in Osijek, Croatia, launched a project called Otvorena mreža ("Open Net"), which creates mobile Wi-Fi hotspots. Open Net volunteers carry the hotspots on their backs — backpacks with mobile Wi-Fi devices in them — where they're most needed; so far, they've been in the border city of Tovarnik, as well as Beli Manastir. A typical mobile Wi-Fi hospot reaches a radius of about several hundred feet.

They say the response has been overwhelmingly positive.

"Many of them haven't heard from their family for days. They don't know where they are," Valent Turković, the project's founder in Croatia, told Mashable. "Most of the time, so many people would surround us, that we didn't even have time to talk to them."

A volunteer with Open Net. Image: Otvorena Mreza

In larger cities, such as Zagreb, 3G Internet is available, but in smaller villages and many of the refugee centers, it collapses when too many people try to connect. That's one of the group's biggest obstacles: the lack of 3G. Turković says that plans for the future include building a sturdier network, one that is independent of local mobile operators, which could function in times of crises like this.

A map of mobile hotspots by Otvorena Mreza in the city of Beli Manastir. Image: Nodes.wlan-si.net

Open Net has been able to help people through Nodewatcher, an open source solution for rapid Wi-Fi hotspot deployment from Slovenia. The next step is providing instructions on which hardware to use and how to set it up, so anyone can build a mobile hotspot quickly — themselves.

Many of the migrants and refugees are also using private messaging systems, such as WhatsApp, to communicate with one another. The app is used to exchange vital information about border crossings and safest paths west.

As the migrant crisis in Europe reaches heights not seen since the post-World War II era, driven in large part by millions of displaced Syrians, refugees are more than ever setting out to find routes into northern Europe. Syrians are not alone in their journey, though, as other migrants from across Africa and the Middle East flood into Europe, seeking jobs and a better life.

Additional reporting by Megan Specia