netperf is a benchmark that can be used to measure the performance of many different types of networking including Unix Domain Sockets and TCP and UDP via BSD Sockets. It provides tests for both unidirectional throughput and end-to-end latency. Netperf page.
bing by Pierre Beyssac determines bandwidth on a point-to-point link by sending ICMP ECHO_REQUEST packets and measuring their roundtrip times for different packet sizes on each end of the link.