add tcpdump example and update building instructions with make

README.md

@@ -4,14 +4,22 @@ Fetch d4-goclient code and dependencies
 go get github.com/D4-project/d4-goclient
 go get github.com/satori/go.uuid
 ```
+Use make to build binaries:
 ```bash
-go build d4-goclient.go
+make arm5l  # for raspberry pi / linux
+make amd64l # for amd64 / linux
 ```
 # Use
 ## Launch a d4-server
 See https://github.com/D4-project/d4-core/tree/master/server
+$IP_SRV being the d4-server's address, $PORT its listening port
 ## Pipe data into the client
-
+###Some file
 ```bash
-cat /proc/cpuinfo | ./d4-goclient -c conf.sample/ |  socat - OPENSSL-CONNECT:127.0.0.1:4443,verify=0
+cat /proc/cpuinfo | ./d4-goclient -c conf.sample/ |  socat - OPENSSL-CONNECT:$IP_SRV:$PORT,verify=0
+```
+###Tcpdump output, discarding our own traffic
+$IP being the monitoring computer ip
+```bash
+tcpdump not dst $IP and not src $IP -w - | ./d4-goclient -c conf.sample/ |  socat - OPENSSL-CONNECT:$IP_SRV:$PORT,verify=0
 ```