netstat is described as 'Displays active TCP connections, ports on which the computer is listening, Ethernet statistics, the IP routing table, IPv4 statistics (for the IP, ICMP, TCP, and UDP protocols), and IPv6 statistics (for the IPv6, ICMPv6, TCP over IPv6, and UDP over IPv6 protocols)'. There are seven alternatives to netstat for a variety of platforms, including Windows, Linux, Online / Web-based, BSD and Self-Hosted solutions. The best alternative is Wireshark, which is both free and Open Source. Other great apps like netstat are Bandwhich (Free, Open Source), iproute2 (Free, Open Source), Local Monitor (Free) and Why Can't I Connect? (Free, Open Source).
Wireshark is the world's foremost network protocol analyzer. It lets you capture and interactively browse the traffic running on a computer network. It is the de facto (and often de jure) standard across many industries and educational institutions.
"Why Can't I Connect?" makes it easier to resolve TCP/IP connection errors. Use it to diagnose connections to common server types (Microsoft SQL Server, MySQL Server, FTP, SFTP, IMAP, POP3, SMTP, IRC, LDAP, Usenet) and create generic TCP/IP clients and / or servers.
Verifies IP-level connectivity to another TCP/IP computer by sending Internet Control Message Protocol (ICMP) Echo Request messages. The receipt of corresponding Echo Reply messages are displayed, along with round-trip times.