diff --git a/api/handler/handler.go b/api/handler/handler.go
index 2b1de88..6704a77 100644
--- a/api/handler/handler.go
+++ b/api/handler/handler.go
@@ -161,6 +161,9 @@ type Host interface {
 	// FuncRemoveHeader with HeaderKindResponseTrailers. This panics if
 	// FeatureTrailers is not supported.
 	RemoveResponseTrailer(ctx context.Context, name string)
+
+	// GetSourceAddr supports the WebAssembly function export FuncGetSourceAddr.
+	GetSourceAddr(ctx context.Context) string
 }
 
 // eofReader is safer than reading from os.DevNull as it can never overrun
@@ -206,3 +209,4 @@ func (UnimplementedHost) GetResponseTrailerValues(context.Context, string) (valu
 func (UnimplementedHost) SetResponseTrailerValue(context.Context, string, string)            {}
 func (UnimplementedHost) AddResponseTrailerValue(context.Context, string, string)            {}
 func (UnimplementedHost) RemoveResponseTrailer(context.Context, string)                      {}
+func (UnimplementedHost) GetSourceAddr(context.Context) string                               { return "1.1.1.1:12345" }
diff --git a/api/handler/wasm.go b/api/handler/wasm.go
index 48c2e48..3608464 100644
--- a/api/handler/wasm.go
+++ b/api/handler/wasm.go
@@ -316,4 +316,10 @@ const (
 	//
 	// TODO: document on http-wasm-abi
 	FuncSetStatusCode = "set_status_code"
+
+	// FuncGetSourceAddr writes the SourceAddr to memory if it isn't larger than BufLimit.
+	// The result is its length in bytes. Ex. "1.1.1.1:12345" or "[fe80::101e:2bdf:8bfb:b97e]:12345"
+	//
+	// TODO: document on http-wasm-abi
+	FuncGetSourceAddr = "get_source_addr"
 )
diff --git a/handler/middleware.go b/handler/middleware.go
index cfdcd37..6cf49d9 100644
--- a/handler/middleware.go
+++ b/handler/middleware.go
@@ -565,6 +565,17 @@ func (m *middleware) writeBody(ctx context.Context, mod wazeroapi.Module, params
 	writeBody(mod, buf, bufLen, w)
 }
 
+// getSourceAddr implements the WebAssembly host function handler.FuncGetSourceAddr.
+func (m *middleware) getSourceAddr(ctx context.Context, mod wazeroapi.Module, stack []uint64) {
+	buf := uint32(stack[0])
+	bufLimit := handler.BufLimit(stack[1])
+
+	method := m.host.GetSourceAddr(ctx)
+	methodLen := writeStringIfUnderLimit(mod.Memory(), buf, bufLimit, method)
+
+	stack[0] = uint64(methodLen)
+}
+
 func writeBody(mod wazeroapi.Module, buf, bufLen uint32, w io.Writer) {
 	// buf_len 0 means to overwrite with nothing
 	var b []byte
@@ -694,6 +705,9 @@ func (m *middleware) instantiateHost(ctx context.Context) (wazeroapi.Module, err
 		WithGoModuleFunction(wazeroapi.GoModuleFunc(m.writeBody), []wazeroapi.ValueType{i32, i32, i32}, []wazeroapi.ValueType{}).
 		WithParameterNames("kind", "body", "body_len").Export(handler.FuncWriteBody).
 		NewFunctionBuilder().
+		WithGoModuleFunction(wazeroapi.GoModuleFunc(m.getSourceAddr), []wazeroapi.ValueType{i32, i32}, []wazeroapi.ValueType{i32}).
+		WithParameterNames("buf", "buf_limit").Export(handler.FuncGetSourceAddr).
+		NewFunctionBuilder().
 		WithGoFunction(wazeroapi.GoFunc(m.getStatusCode), []wazeroapi.ValueType{}, []wazeroapi.ValueType{i32}).
 		WithParameterNames().Export(handler.FuncGetStatusCode).
 		NewFunctionBuilder().
diff --git a/handler/nethttp/host.go b/handler/nethttp/host.go
index a73e3f5..8ea2538 100644
--- a/handler/nethttp/host.go
+++ b/handler/nethttp/host.go
@@ -346,3 +346,9 @@ func addTrailer(header http.Header, name string, value string) {
 func removeTrailer(header http.Header, name string) {
 	header.Del(http.TrailerPrefix + name)
 }
+
+// GetSourceAddr implements the same method as documented on handler.Host.
+func (host) GetSourceAddr(ctx context.Context) string {
+	r := requestStateFromContext(ctx).r
+	return r.RemoteAddr
+}
diff --git a/handler/nethttp/host_test.go b/handler/nethttp/host_test.go
index 1660fee..ff22a80 100644
--- a/handler/nethttp/host_test.go
+++ b/handler/nethttp/host_test.go
@@ -17,6 +17,7 @@ func Test_host(t *testing.T) {
 	newCtx := func(features handler.Features) (context.Context, handler.Features) {
 		// The below configuration supports all features.
 		r, _ := http.NewRequest("GET", "", bytes.NewReader(nil))
+		r.RemoteAddr = "1.2.3.4:12345"
 		w := &bufferingResponseWriter{delegate: &httptest.ResponseRecorder{HeaderMap: map[string][]string{}}}
 		return context.WithValue(testCtx, requestStateKey{}, &requestState{r: r, w: w}), features
 	}
diff --git a/tck/guest/go.mod b/tck/guest/go.mod
index 1240234..874707f 100644
--- a/tck/guest/go.mod
+++ b/tck/guest/go.mod
@@ -2,4 +2,4 @@ module github.com/anuraaga/http-wasm-tck/guest
 
 go 1.19
 
-require github.com/http-wasm/http-wasm-guest-tinygo v0.1.1
+require github.com/http-wasm/http-wasm-guest-tinygo v0.3.1-0.20231031134125-487a6e2eec5e
diff --git a/tck/guest/go.sum b/tck/guest/go.sum
index 5e83e86..e1769d0 100644
--- a/tck/guest/go.sum
+++ b/tck/guest/go.sum
@@ -1,2 +1,2 @@
-github.com/http-wasm/http-wasm-guest-tinygo v0.1.1 h1:7L+MhMNDVsUAqmElG64JEZ0n1yGCKTx0w01N1b08Xhc=
-github.com/http-wasm/http-wasm-guest-tinygo v0.1.1/go.mod h1:roTs1mkyGDe1CUzrL8JUXSbPNYUHnnWKMCG6epmRAZY=
+github.com/http-wasm/http-wasm-guest-tinygo v0.3.1-0.20231031134125-487a6e2eec5e h1:mUEuIuH+XAtp5tkJPpwN5ZAtgvt64tYaYsk/KoK42lQ=
+github.com/http-wasm/http-wasm-guest-tinygo v0.3.1-0.20231031134125-487a6e2eec5e/go.mod h1:zcKr7h/t5ha2ZWIMwV4iOqhfC/qno/tNPYgybVkn/MQ=
diff --git a/tck/guest/main.go b/tck/guest/main.go
index af9e147..fecbeac 100644
--- a/tck/guest/main.go
+++ b/tck/guest/main.go
@@ -104,6 +104,8 @@ func (h *handler) handleRequest(req api.Request, resp api.Response) (next bool,
 		next, reqCtx = h.testReadBody(req, resp, strings.Repeat("a", 4096))
 	case "read_body/request/xlarge":
 		next, reqCtx = h.testReadBody(req, resp, strings.Repeat("a", 5000))
+	case "get_source_addr":
+		next, reqCtx = h.testGetSourceAddr(req, resp, "127.0.0.1")
 	default:
 		fail(resp, "unknown x-httpwasm-test-id")
 	}
@@ -214,6 +216,24 @@ func (h *handler) testReadBody(req api.Request, resp api.Response, expectedBody
 	return true, 0
 }
 
+func (h *handler) testGetSourceAddr(req api.Request, resp api.Response, expectedAddr string) (next bool, reqCtx uint32) {
+	addr := req.GetSourceAddr()
+	raw := strings.Split(addr, ":")
+	if len(raw) != 2 {
+		fail(resp, fmt.Sprintf("get_source_addr: unknown colon count %s", req.GetSourceAddr()))
+		return
+	}
+	if raw[0] != expectedAddr {
+		fail(resp, fmt.Sprintf("get_source_addr: want %s, have %s", expectedAddr, req.GetSourceAddr()))
+		return
+	}
+	if len(raw[1]) <= 0 || len(raw[1]) > 5 {
+		fail(resp, fmt.Sprintf("get_source_addr: could not find port number '%s' from %s", raw[1], req.GetSourceAddr()))
+		return
+	}
+	return true, 0
+}
+
 func fail(resp api.Response, msg string) {
 	resp.SetStatusCode(500)
 	resp.Headers().Set("x-httpwasm-tck-failed", msg)
diff --git a/tck/run.go b/tck/run.go
index 0044a05..568c60a 100644
--- a/tck/run.go
+++ b/tck/run.go
@@ -53,6 +53,7 @@ func Run(t *testing.T, client *http.Client, url string) {
 	r.testAddHeaderValueRequest()
 	r.testRemoveHeaderRequest()
 	r.testReadBodyRequest()
+	r.testGetSourceAddr()
 }
 
 type testRunner struct {
@@ -493,6 +494,24 @@ func (r *testRunner) testRemoveHeaderRequest() {
 	}
 }
 
+func (r *testRunner) testGetSourceAddr() {
+	hostFn := handler.FuncGetSourceAddr
+
+	r.t.Run(hostFn, func(t *testing.T) {
+		req, err := http.NewRequest("GET", r.url, nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		req.Header.Set("x-httpwasm-tck-testid", hostFn)
+		resp, err := r.client.Do(req)
+		if err != nil {
+			t.Error(err)
+		}
+		checkResponse(t, resp)
+	})
+}
+
 func checkResponse(t *testing.T, resp *http.Response) string {
 	t.Helper()
 
diff --git a/tck/tck.wasm b/tck/tck.wasm
index ac0fb21..fc70d1b 100755
Binary files a/tck/tck.wasm and b/tck/tck.wasm differ
diff --git a/testing/handlertest/testhandler.go b/testing/handlertest/testhandler.go
index e382c46..2392a0d 100644
--- a/testing/handlertest/testhandler.go
+++ b/testing/handlertest/testhandler.go
@@ -49,6 +49,7 @@ func HostTest(t *testing.T, h handler.Host, newCtx func(handler.Features) (conte
 	ht.testResponseHeaders()
 	ht.testResponseBody()
 	ht.testResponseTrailers()
+	ht.testSourceAddr()
 
 	if len(ht.errText) == 0 {
 		return nil
@@ -64,6 +65,18 @@ type hostTester struct {
 	errText []byte
 }
 
+func (h *hostTester) testSourceAddr() {
+	ctx, _ := h.newCtx(0) // no features required
+
+	h.t.Run("GetSourceAddr", func(t *testing.T) {
+		addr := h.h.GetSourceAddr(ctx)
+		want := "1.2.3.4:12345"
+		if addr != want {
+			t.Errorf("unexpected default source addr, want: %v, have: %v", want, addr)
+		}
+	})
+}
+
 func (h *hostTester) testMethod() {
 	ctx, _ := h.newCtx(0) // no features required