netcat - Netcat is a featured networking utility which reads and writes data across network connections...

Cell Signal Monitor - Cell Signal Monitor is an advanced network monitor that helps you to watch the state of cellular network by gathering data about cell towers. The app supports GSM, UMTS and LTE networks. There is a Free edition with adds.

Wireshark - Wireshark is a network protocol analyzer for Unix and Windows. It lets you capture and interactively browse the traffic running on a computer network.

OpenSignal - Mobile analytics and insights on wireless connectivity from Opensignal, the independent global standard for understanding the true state of the world's mobile network.

SmartSniff - SmartSniff is a packet sniffer that capture TCP/IP packets and display them as sequence of conversations between clients and servers.

NetMonster - NetMonster is a networking app by Michal Mrocek that comes up with features to enable you to get detailed information about your current network right on your mobile phone screen.