Iperf bidirectional bandwidth measurement

Question

Server side:

# iperf -s
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
[  4] local 192.168.24.243 port 5001 connected with 192.168.24.242 port 44809
[ ID] Interval       Transfer     Bandwidth
[  4]  0.0-10.1 sec   113 MBytes  94.1 Mbits/sec
connect failed: Connection refused

Client side:

# iperf -c 192.168.24.243 -r
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
------------------------------------------------------------
Client connecting to 192.168.24.243, TCP port 5001
TCP window size:  123 KByte (default)
------------------------------------------------------------
[  5] local 192.168.24.242 port 44809 connected with 192.168.24.243 port 5001
Waiting for server threads to complete. Interrupt again to force quit.
[ ID] Interval       Transfer     Bandwidth
[  5]  0.0-10.0 sec   113 MBytes  94.8 Mbits/sec

Why do I get this error? There's no firewall.

Solution

Looks like your client is blocking the incoming connection from the server.

The server is reporting "Connection refused".
The client is reporting "Waiting for server threads to complete".

Comments

[Alexander Janssen]

For an easy test add a (temporary) Netfilter rule to the INPUT-chain: iptables -t filter -I INPUT -s 192.168.24.243 -p tcp --dport 5001 -j ACCEPT on host 192.168.24.242.