server: Change server startup message. (#2195)

This change brings in the new agreed startup message
for the server.

Adds additional links point to Minio SDKs as well.

checkport.go

@@ -0,0 +1,93 @@
+/*
+ * Minio Cloud Storage, (C) 2016 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package main
+
+import (
+	"errors"
+	"net"
+	"os"
+	"syscall"
+)
+
+// Make sure that none of the other processes are listening on the
+// specified port on any of the interfaces.
+//
+// On linux if a process is listening on 127.0.0.1:9000 then Listen()
+// on ":9000" fails with the error "port already in use".
+// However on Mac OSX Listen() on ":9000" falls back to the IPv6 address.
+// This causes confusion on Mac OSX that minio server is not reachable
+// on 127.0.0.1 even though minio server is running. So before we start
+// the minio server we make sure that the port is free on all the IPs.
+func checkPortAvailability(port int) {
+	isAddrInUse := func(err error) bool {
+		// Check if the syscall error is EADDRINUSE.
+		// EADDRINUSE is the system call error if another process is
+		// already listening at the specified port.
+		neterr, ok := err.(*net.OpError)
+		if !ok {
+			return false
+		}
+		osErr, ok := neterr.Err.(*os.SyscallError)
+		if !ok {
+			return false
+		}
+		sysErr, ok := osErr.Err.(syscall.Errno)
+		if !ok {
+			return false
+		}
+		if sysErr != syscall.EADDRINUSE {
+			return false
+		}
+		return true
+	}
+	ifcs, err := net.Interfaces()
+	if err != nil {
+		fatalIf(err, "Unable to list interfaces.")
+	}
+	for _, ifc := range ifcs {
+		addrs, err := ifc.Addrs()
+		if err != nil {
+			fatalIf(err, "Unable to list addresses on interface %s.", ifc.Name)
+		}
+		for _, addr := range addrs {
+			ipnet, ok := addr.(*net.IPNet)
+			if !ok {
+				errorIf(errors.New(""), "Failed to assert type on (*net.IPNet) interface.")
+				continue
+			}
+			ip := ipnet.IP
+			network := "tcp4"
+			if ip.To4() == nil {
+				network = "tcp6"
+			}
+			tcpAddr := net.TCPAddr{IP: ip, Port: port, Zone: ifc.Name}
+			l, err := net.ListenTCP(network, &tcpAddr)
+			if err != nil {
+				if isAddrInUse(err) {
+					// Fail if port is already in use.
+					fatalIf(err, "Unable to listen on %s:%.d.", tcpAddr.IP, tcpAddr.Port)
+				} else {
+					// Ignore other errors.
+					continue
+				}
+			}
+			if err = l.Close(); err != nil {
+				fatalIf(err, "Unable to close listener on %s:%.d.", tcpAddr.IP, tcpAddr.Port)
+			}
+		}
+	}
+}