Creating a Portable WiFi with Raspberry Pi 3+

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For friends who travel frequently, hotel WiFi issues are often a hassle. Hotel WiFi signals are weak, insecure, slow, and often disconnect. Alternatively, the configuration may be poor, unable to support a certain number of clients, and often cannot obtain an IP address. In this case, a portable WiFi can help you.

A portable WiFi allows you to share a wired network via WiFi, creating a temporary wireless local area network that connects to the internet. On this basis, a WiFi hotspot network is established for one or more wireless internet terminals, facilitating mobile office work and providing internet access for business trips and travel. The portable WiFi is secure as it is a private wireless network for the user, avoiding the risks of information leakage from using public WiFi. Moreover, it is easy to operate, requiring no setup and can be used immediately upon powering on. Below, I will guide you step by step to turn your Raspberry Pi into a portable WiFi.

There are many ways to convert Raspberry Pi 3 into a portable WiFi. I mainly use two methods: bridge mode and building a router based on openWrt.

First, we will implement bridge mode, which requires installing some third-party software, with the core software being Hostapd. Hostapd is an open-source project, a user-space daemon for wireless access points (AP) and authentication servers. Hostapd implements IEEE802.11 AP management, IEEE802.1X/WPA/WPA2/EAP authentication, RADIUS client, EAP server, and RADIUS authorization server, supporting Linux system host AP, madwifi, and mac80211-based drivers. 1. Install the required programs: sudo apt-get install hostapd udhcpd sudo apt-get install bridge-utils

2. Configure the network card by editing the network configuration file: sudo vim /etc/network/interfaces Comment out all configurations related to the wireless network card, as shown below: #allow-hotplug wlan0#iface wlan0 inet manual# wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf#allow-hotplug wlan1#iface wlan0 inet manual# wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

Add the bridge configuration to the file: auto br0 iface br0 inet dhcp bridge_ports eth0 wlan0 The final configuration mainly consists of the following parts: // Loopback network configuration auto lo iface lo inet loopback // Wired network card configuration iface eth0 inet dhcp # Bridge configuration auto br0 iface br0 inet dhcp bridge_ports eth0 wlan0

3. Configure hostapd sudo vim /etc/hostapd/hostapd.conf Configuration information as follows: interface=wlan0 driver=nl80211 bridge=br0 ssid=Raspberry_AP channel=1 wmm_enabled=0 wpa=1 wpa_passphrase=testforap wpa_key_mgmt=WPA-PSK wpa_pairwise=TKIP rsn_pairwise=CCMP auth_algs=1 macaddr_acl=0 ssid=Raspberry_AP Set the AP’s SSID and wpa_passphrase=testforap to set the password for connecting to the AP as testforap, then save the configuration file.

4. Restart and test hostapd sudo reboot After rebooting, use the following command to test if hostapd is working properly: sudo hostapd -dd /etc/hostapd/hostapd.conf

If there are no errors, the mobile device should be able to search for the configured wireless AP. Then press Ctrl+C to exit this test.

Once the previous steps are successfully completed, the last step is to set the path of the hostapd configuration file. sudo vim /etc/default/hostapd Remove the comment symbol # from the line DAEMON_CONF, and change it to our configuration file path: DAEMON_CONF="/etc/hostapd/hostapd.conf" Add hostapd to startup sudo update-rc.d hostapd enable 5. Restart and test hostapd Restart the hostapd service sudo service hostapd restart Open the mobile WiFi, search and connect to Raspberry_AP.

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The configuration process for bridge mode is quite simple. Next, I will introduce how to use openwrt to build a more powerful wireless router.

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