diff --git a/README.rst b/README.rst
index ad594cf..8d11ae7 100644
--- a/README.rst
+++ b/README.rst
@@ -186,8 +186,9 @@ threads
 cpu_percent
 cpu_affinity
 memory_percent
+parent              x            x
 children
-connections
+connections         x            x
 is_running
 ================ ===== ======= ====== =======
 
@@ -231,7 +232,6 @@ hostname              x     x      x       x
   - wait_procs
   - Process class
 
-    - parent (use ppid instead)
     - as_dict
     - wait
 
diff --git a/common/common_darwin.go b/common/common_darwin.go
index cc74601..6cdefb4 100644
--- a/common/common_darwin.go
+++ b/common/common_darwin.go
@@ -74,6 +74,10 @@ func CallLsof(invoke Invoker, pid int32, args ...string) ([]string, error) {
 	}
 	out, err := invoke.Command(lsof, cmd...)
 	if err != nil {
+		// if not pid found, lsof returnes code 1
+		if err.Error() == "exit status 1" && len(out) == 0 {
+			return []string{}, nil
+		}
 		return []string{}, err
 	}
 	lines := strings.Split(string(out), "\n")
diff --git a/common/common_linux.go b/common/common_linux.go
index 3c760e5..bfd96a9 100644
--- a/common/common_linux.go
+++ b/common/common_linux.go
@@ -8,6 +8,8 @@ import (
 	"strings"
 )
 
+// CallLsof invokes lsof to get connection informations.
+// This is same as darwin currently.
 func CallLsof(invoke Invoker, pid int32, args ...string) ([]string, error) {
 	var cmd []string
 	if pid == 0 { // will get from all processes.
@@ -22,6 +24,10 @@ func CallLsof(invoke Invoker, pid int32, args ...string) ([]string, error) {
 	}
 	out, err := invoke.Command(lsof, cmd...)
 	if err != nil {
+		// if not pid found, lsof returnes code 1
+		if err.Error() == "exit status 1" && len(out) == 0 {
+			return []string{}, nil
+		}
 		return []string{}, err
 	}
 	lines := strings.Split(string(out), "\n")
diff --git a/net/net_darwin.go b/net/net_darwin.go
index da722dc..bcf2915 100644
--- a/net/net_darwin.go
+++ b/net/net_darwin.go
@@ -91,8 +91,13 @@ func NetIOCounters(pernic bool) ([]NetIOCountersStat, error) {
 	return ret, nil
 }
 
-// Return a list of network connections opened by a process
+// Return a list of network connections opened.
 func NetConnections(kind string) ([]NetConnectionStat, error) {
+	return NetConnectionsPid(kind, 0)
+}
+
+// Return a list of network connections opened by a process.
+func NetConnectionsPid(kind string, pid int32) ([]NetConnectionStat, error) {
 	var ret []NetConnectionStat
 
 	args := []string{"-i"}
@@ -126,7 +131,7 @@ func NetConnections(kind string) ([]NetConnectionStat, error) {
 	}
 
 	// we can not use -F filter to get all of required information at once.
-	r, err := common.CallLsof(invoke, 0, args...)
+	r, err := common.CallLsof(invoke, pid, args...)
 	if err != nil {
 		return nil, err
 	}
diff --git a/net/net_linux.go b/net/net_linux.go
index de0d65a..6e54244 100644
--- a/net/net_linux.go
+++ b/net/net_linux.go
@@ -90,7 +90,13 @@ func NetIOCounters(pernic bool) ([]NetIOCountersStat, error) {
 	return ret, nil
 }
 
+// Return a list of network connections opened.
 func NetConnections(kind string) ([]NetConnectionStat, error) {
+	return NetConnectionsPid(kind, 0)
+}
+
+// Return a list of network connections opened by a process.
+func NetConnectionsPid(kind string, pid int32) ([]NetConnectionStat, error) {
 	var ret []NetConnectionStat
 
 	args := []string{"-i"}
@@ -124,7 +130,7 @@ func NetConnections(kind string) ([]NetConnectionStat, error) {
 	}
 
 	// we can not use -F filter to get all of required information at once.
-	r, err := common.CallLsof(invoke, 0, args...)
+	r, err := common.CallLsof(invoke, pid, args...)
 	if err != nil {
 		return nil, err
 	}
diff --git a/process/process_darwin.go b/process/process_darwin.go
index 634d5cf..dab9f13 100644
--- a/process/process_darwin.go
+++ b/process/process_darwin.go
@@ -286,7 +286,7 @@ func (p *Process) OpenFiles() ([]OpenFilesStat, error) {
 }
 
 func (p *Process) Connections() ([]net.NetConnectionStat, error) {
-	return nil, common.NotImplementedError
+	return net.NetConnectionsPid("all", p.Pid)
 }
 
 func (p *Process) IsRunning() (bool, error) {
diff --git a/process/process_linux.go b/process/process_linux.go
index 79039bf..e108518 100644
--- a/process/process_linux.go
+++ b/process/process_linux.go
@@ -211,7 +211,7 @@ func (p *Process) OpenFiles() ([]OpenFilesStat, error) {
 }
 
 func (p *Process) Connections() ([]net.NetConnectionStat, error) {
-	return nil, common.NotImplementedError
+	return net.NetConnectionsPid("all", p.Pid)
 }
 
 func (p *Process) IsRunning() (bool, error) {
diff --git a/process/process_test.go b/process/process_test.go
index dba0ed9..3d6ee34 100644
--- a/process/process_test.go
+++ b/process/process_test.go
@@ -97,7 +97,7 @@ func Test_Process_MemoryInfo(t *testing.T) {
 
 	v, err := p.MemoryInfo()
 	if err != nil {
-		t.Errorf("geting ppid error %v", err)
+		t.Errorf("geting memory info error %v", err)
 	}
 	empty := MemoryInfoStat{}
 	if v == nil || *v == empty {
@@ -110,7 +110,7 @@ func Test_Process_CmdLine(t *testing.T) {
 
 	v, err := p.Cmdline()
 	if err != nil {
-		t.Errorf("geting ppid error %v", err)
+		t.Errorf("geting cmdline error %v", err)
 	}
 	if !strings.Contains(v, "process.test") {
 		t.Errorf("invalid cmd line %v", v)
@@ -134,7 +134,7 @@ func Test_Process_Status(t *testing.T) {
 
 	v, err := p.Status()
 	if err != nil {
-		t.Errorf("geting ppid error %v", err)
+		t.Errorf("geting status error %v", err)
 	}
 	if !strings.HasPrefix(v, "S") && v != "running" && v != "sleeping" {
 		t.Errorf("could not get state %v", v)
@@ -289,3 +289,18 @@ func Test_Parent(t *testing.T) {
 		t.Fatalf("wrong parent pid")
 	}
 }
+
+func Test_Connections(t *testing.T) {
+	p := testGetProcess()
+
+	c, err := p.Connections()
+	if err != nil {
+		t.Fatalf("error %v", err)
+	}
+	// TODO:
+	// Since go test open no conneciton, ret is empty.
+	// should invoke child process or other solutions.
+	if len(c) != 0 {
+		t.Fatalf("wrong connections")
+	}
+}