diff --git a/tests/Makefile b/tests/Makefile
index 568651e..50e4525 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -10,7 +10,7 @@ LIBS = -lthread -lbio $(FT_LIBS) $(IBUS_LIBS)
 PROG = unit_test
 TESTSRC = unit_test.c test_util.c str_test.c hash_test.c trie_test.c \
 	ko_test.c vi_test.c engine_test.c dict_test.c ipc_test.c \
-	popup_test.c font_test.c ibus_test.c
+	popup_test.c font_test.c ibus_test.c server_test.c
 TESTOBJ = $(TESTSRC:.c=.o)
 PARENTSRC = str.c hash.c trie.c dict.c ko.c vi.c ipc.c popup_layout.c \
 	font.c
@@ -29,6 +29,7 @@ $(TESTOBJ): test.h ../dat.h ../fn.h ../ipc.h ../cutest/cutest.h
 engine_test.o: ../strans.c
 ibus_test.o: CFLAGS += $(IBUS_CFLAGS)
 ibus_test.o: ../ibus.c
+server_test.o: ../srv.c
 unit_font.o: CFLAGS += $(FT_CFLAGS)
 
 unit_%.o: ../%.c ../dat.h ../fn.h ../ipc.h
diff --git a/tests/engine_test.c b/tests/engine_test.c
index 508071a..8148eb0 100644
--- a/tests/engine_test.c
+++ b/tests/engine_test.c
@@ -9,6 +9,31 @@ Str shownpre(Im*);
 
 static int typekeys(struct ct*, char*, Str*);
 
+void
+testengineinit(int lang)
+{
+	init();
+	im.l = getlang(lang);
+}
+
+void
+testenginehandle(Keyreq *req)
+{
+	imhandlekey(req);
+}
+
+void*
+testengineowner(void)
+{
+	return activeowner;
+}
+
+void
+testenginepreedit(Str *preedit)
+{
+	impre(preedit);
+}
+
 void
 vietnamese_state_lifetime(struct ct *t)
 {
diff --git a/tests/server_test.c b/tests/server_test.c
new file mode 100644
index 0000000..bc55b9f
--- /dev/null
+++ b/tests/server_test.c
@@ -0,0 +1,370 @@
+#include <errno.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include "../srv.c"
+#include "../cutest/cutest.h"
+
+void	testengineinit(int);
+void	testenginehandle(Keyreq*);
+void*	testengineowner(void);
+void	testenginepreedit(Str*);
+
+#undef recv
+
+typedef struct Enginegate Enginegate;
+typedef struct Testclient Testclient;
+
+struct Enginegate
+{
+	Channel	*seen;
+	Channel	*go;
+	Channel	*stop;
+	Channel	*done;
+};
+
+struct Testclient
+{
+	int	fd;
+	int	peer;
+	dev_t	dev;
+	ino_t	ino;
+	Channel	*done;
+};
+
+static void
+enginegate(void *arg)
+{
+	Enginegate *g;
+	Keyreq req;
+	uchar token;
+	Alt alts[] = {
+		{keyc, &req, CHANRCV, nil},
+		{nil, &token, CHANRCV, nil},
+		{nil, nil, CHANEND, nil},
+	};
+
+	g = arg;
+	alts[1].c = g->stop;
+	for(;;)
+		switch(alt(alts)){
+		case 0:
+			chansend(g->seen, &req);
+			chanrecv(g->go, &token);
+			testenginehandle(&req);
+			break;
+		case 1:
+			chansend(g->done, &token);
+			return;
+		}
+}
+
+static void
+clientproc(void *arg)
+{
+	Testclient *client;
+	uchar token;
+
+	client = arg;
+	clientthread((void*)(uintptr)client->fd);
+	token = 0;
+	chansend(client->done, &token);
+}
+
+static int
+startclient(struct ct *t, Testclient *client)
+{
+	struct stat st;
+	int fd[2];
+	uchar token;
+
+	memset(client, 0, sizeof *client);
+	client->fd = -1;
+	client->peer = -1;
+	if(socketpair(AF_UNIX, SOCK_STREAM, 0, fd) < 0)
+		return CT_ERRORF(t, "socketpair failed: %s", strerror(errno));
+	client->fd = fd[0];
+	client->peer = fd[1];
+	if(fstat(client->fd, &st) < 0){
+		close(client->fd);
+		close(client->peer);
+		client->fd = -1;
+		client->peer = -1;
+		return CT_ERRORF(t, "socket stat failed: %s", strerror(errno));
+	}
+	client->dev = st.st_dev;
+	client->ino = st.st_ino;
+	client->done = chancreate(sizeof token, 0);
+	token = 0;
+	if(channbsend(clientc, &token) <= 0){
+		close(client->fd);
+		close(client->peer);
+		chanfree(client->done);
+		client->fd = -1;
+		client->peer = -1;
+		client->done = nil;
+		return CT_ERRORF(t, "client slot unavailable");
+	}
+	if(proccreate(clientproc, client, 8192) < 0){
+		chanrecv(clientc, &token);
+		close(client->fd);
+		close(client->peer);
+		chanfree(client->done);
+		client->fd = -1;
+		client->peer = -1;
+		client->done = nil;
+		return CT_ERRORF(t, "client worker creation failed");
+	}
+	return 1;
+}
+
+static int
+sendkey(struct ct *t, Testclient *client, int want, u32int mod, u32int key)
+{
+	uchar req[Ipcreqsz];
+
+	ipcpackreq(req, want, mod, key);
+	if(ipcsend(client->peer, req, sizeof req) == 0)
+		return 1;
+	return CT_ERRORF(t, "request send failed: %s", strerror(errno));
+}
+
+static int
+sendreset(struct ct *t, Testclient *client, int want)
+{
+	uchar req[Ipcreqsz];
+
+	ipcpackreset(req, want);
+	if(ipcsend(client->peer, req, sizeof req) == 0)
+		return 1;
+	return CT_ERRORF(t, "reset send failed: %s", strerror(errno));
+}
+
+static Keyreq
+nextrequest(struct ct *t, Enginegate *g, int op)
+{
+	Keyreq req;
+
+	memset(&req, 0, sizeof req);
+	chanrecv(g->seen, &req);
+	CT_EQ_INT(t, op, req.op);
+	return req;
+}
+
+static void
+allowrequest(Enginegate *g)
+{
+	uchar token;
+
+	token = 0;
+	chansend(g->go, &token);
+}
+
+static int
+readreply(struct ct *t, Testclient *client, int want, char *preedit, int npreedit)
+{
+	char commit[Maxutf];
+	Ipcresp resp;
+
+	if(ipcreadresp(client->peer, want, commit, sizeof commit,
+	   preedit, npreedit, &resp) < 0)
+		return CT_ERRORF(t, "response read failed: %s", strerror(errno));
+	CT_EQ_STR(t, "", commit);
+	return resp.eaten;
+}
+
+static void
+waitclient(struct ct *t, Testclient *client)
+{
+	struct stat st;
+	uchar token;
+
+	chanrecv(client->done, &token);
+	errno = 0;
+	if(fstat(client->fd, &st) == 0)
+		CT_CHECK(t, st.st_dev != client->dev || st.st_ino != client->ino);
+	else
+		CT_EQ_INT(t, EBADF, errno);
+	chanfree(client->done);
+	client->done = nil;
+}
+
+static void
+disconnectclient(struct ct *t, Enginegate *g, Testclient *client, void *owner)
+{
+	Keyreq req;
+	uchar token;
+
+	close(client->peer);
+	client->peer = -1;
+	req = nextrequest(t, g, Keyrelease);
+	if(owner != nil)
+		CT_EQ_PTR(t, owner, req.owner);
+	CT_CHECK(t, channbrecv(client->done, &token) <= 0);
+	allowrequest(g);
+	waitclient(t, client);
+}
+
+void
+server_connection_ownership(struct ct *t)
+{
+	Channel *oldclientc;
+	Enginegate gate;
+	Testclient a, b, c;
+	Keyreq req;
+	Drawcmd dc;
+	Str shown;
+	char preedit[Maxutf];
+	void *aowner, *bowner, *cowner;
+	uchar byte, token;
+	ssize_t n;
+	int gateactive;
+
+	memset(&gate, 0, sizeof gate);
+	memset(&a, 0, sizeof a);
+	memset(&b, 0, sizeof b);
+	memset(&c, 0, sizeof c);
+	a.fd = a.peer = b.fd = b.peer = c.fd = c.peer = -1;
+	aowner = bowner = cowner = nil;
+	oldclientc = clientc;
+	while(channbrecv(drawc, &dc) > 0)
+		;
+	clientc = chancreate(sizeof token, 3);
+	gate.seen = chancreate(sizeof(Keyreq), 0);
+	gate.go = chancreate(sizeof token, 0);
+	gate.stop = chancreate(sizeof token, 0);
+	gate.done = chancreate(sizeof token, 0);
+	testengineinit(LangJP);
+	gateactive = proccreate(enginegate, &gate, 8192) >= 0;
+	if(!CT_CHECK(t, gateactive))
+		goto cleanup;
+	if(!startclient(t, &a) || !startclient(t, &b))
+		goto cleanup;
+
+	if(!sendkey(t, &a, 1, 0, 'k'))
+		goto cleanup;
+	req = nextrequest(t, &gate, Keypress);
+	aowner = req.owner;
+	allowrequest(&gate);
+	CT_CHECK(t, readreply(t, &a, 1, preedit, sizeof preedit));
+	CT_EQ_STR(t, "k", preedit);
+	if(!sendkey(t, &a, 1, 0, 'a'))
+		goto cleanup;
+	req = nextrequest(t, &gate, Keypress);
+	CT_EQ_PTR(t, aowner, req.owner);
+	allowrequest(&gate);
+	CT_CHECK(t, readreply(t, &a, 1, preedit, sizeof preedit));
+	CT_EQ_STR(t, "か", preedit);
+	CT_EQ_PTR(t, aowner, testengineowner());
+
+	if(!sendkey(t, &b, 1, 0, 'n'))
+		goto cleanup;
+	req = nextrequest(t, &gate, Keypress);
+	bowner = req.owner;
+	CT_CHECK(t, bowner != aowner);
+	allowrequest(&gate);
+	CT_CHECK(t, readreply(t, &b, 1, preedit, sizeof preedit));
+	CT_EQ_STR(t, "ん", preedit);
+	CT_EQ_PTR(t, bowner, testengineowner());
+
+	if(!sendreset(t, &a, 1))
+		goto cleanup;
+	req = nextrequest(t, &gate, Keyreset);
+	CT_EQ_PTR(t, aowner, req.owner);
+	allowrequest(&gate);
+	CT_CHECK(t, readreply(t, &a, 1, preedit, sizeof preedit));
+	CT_EQ_STR(t, "", preedit);
+	CT_EQ_PTR(t, bowner, testengineowner());
+	if(!sendkey(t, &b, 1, 0, Kmodfirst))
+		goto cleanup;
+	req = nextrequest(t, &gate, Keypress);
+	allowrequest(&gate);
+	CT_CHECK(t, !readreply(t, &b, 1, preedit, sizeof preedit));
+	CT_EQ_STR(t, "ん", preedit);
+
+	disconnectclient(t, &gate, &a, aowner);
+	CT_EQ_PTR(t, bowner, testengineowner());
+	if(!sendkey(t, &b, 1, 0, 'y'))
+		goto cleanup;
+	req = nextrequest(t, &gate, Keypress);
+	allowrequest(&gate);
+	CT_CHECK(t, readreply(t, &b, 1, preedit, sizeof preedit));
+	if(!sendkey(t, &b, 1, 0, 'a'))
+		goto cleanup;
+	req = nextrequest(t, &gate, Keypress);
+	allowrequest(&gate);
+	CT_CHECK(t, readreply(t, &b, 1, preedit, sizeof preedit));
+	CT_EQ_STR(t, "にゃ", preedit);
+
+	if(!sendreset(t, &b, 1))
+		goto cleanup;
+	req = nextrequest(t, &gate, Keyreset);
+	CT_EQ_PTR(t, bowner, req.owner);
+	allowrequest(&gate);
+	CT_CHECK(t, readreply(t, &b, 1, preedit, sizeof preedit));
+	CT_EQ_STR(t, "", preedit);
+	CT_EQ_PTR(t, bowner, testengineowner());
+
+	if(!sendkey(t, &b, 0, 0, 'k'))
+		goto cleanup;
+	req = nextrequest(t, &gate, Keypress);
+	CT_EQ_PTR(t, bowner, req.owner);
+	allowrequest(&gate);
+	CT_CHECK(t, readreply(t, &b, 0, nil, 0));
+	errno = 0;
+	n = recv(b.peer, &byte, 1, MSG_PEEK|MSG_DONTWAIT);
+	CT_EQ_INT(t, -1, n);
+	CT_CHECK(t, errno == EAGAIN || errno == EWOULDBLOCK);
+	CT_EQ_PTR(t, bowner, testengineowner());
+	if(!sendkey(t, &b, 1, 0, 'a'))
+		goto cleanup;
+	req = nextrequest(t, &gate, Keypress);
+	allowrequest(&gate);
+	CT_CHECK(t, readreply(t, &b, 1, preedit, sizeof preedit));
+	CT_EQ_STR(t, "か", preedit);
+
+	disconnectclient(t, &gate, &b, bowner);
+	CT_EQ_PTR(t, nil, testengineowner());
+	testenginepreedit(&shown);
+	CT_EQ_INT(t, 0, shown.n);
+
+	if(!startclient(t, &c))
+		goto cleanup;
+	if(!sendkey(t, &c, 1, 0, 'k'))
+		goto cleanup;
+	req = nextrequest(t, &gate, Keypress);
+	cowner = req.owner;
+	close(c.peer);
+	c.peer = -1;
+	allowrequest(&gate);
+	req = nextrequest(t, &gate, Keyrelease);
+	CT_EQ_PTR(t, cowner, req.owner);
+	CT_EQ_PTR(t, cowner, testengineowner());
+	CT_CHECK(t, channbrecv(c.done, &token) <= 0);
+	allowrequest(&gate);
+	waitclient(t, &c);
+	CT_EQ_PTR(t, nil, testengineowner());
+	CT_CHECK(t, channbrecv(clientc, &token) <= 0);
+
+cleanup:
+	if(a.peer >= 0)
+		disconnectclient(t, &gate, &a, aowner);
+	if(b.peer >= 0)
+		disconnectclient(t, &gate, &b, bowner);
+	if(c.peer >= 0)
+		disconnectclient(t, &gate, &c, cowner);
+	if(gateactive){
+		token = 0;
+		chansend(gate.stop, &token);
+		chanrecv(gate.done, &token);
+	}
+	chanfree(gate.seen);
+	chanfree(gate.go);
+	chanfree(gate.stop);
+	chanfree(gate.done);
+	chanfree(clientc);
+	clientc = oldclientc;
+	while(channbrecv(drawc, &dc) > 0)
+		;
+}
diff --git a/tests/test.h b/tests/test.h
index 9aeee02..8267bfc 100644
--- a/tests/test.h
+++ b/tests/test.h
@@ -70,4 +70,5 @@ void	ipc_response_empty_and_preedit(struct ct*);
 void	ipc_response_max_and_drain(struct ct*);
 void	ipc_response_fragmented_and_truncated(struct ct*);
 void	ipc_broken_peer_send(struct ct*);
+void	server_connection_ownership(struct ct*);
 void	ibus_context_lifecycle(struct ct*);
diff --git a/tests/unit_test.c b/tests/unit_test.c
index ecae4df..636f2ed 100644
--- a/tests/unit_test.c
+++ b/tests/unit_test.c
@@ -124,6 +124,7 @@ static const struct ct_test tests[] = {
 	{ "ipc/response-max-drain", ipc_response_max_and_drain },
 	{ "ipc/response-fragmented-truncated", ipc_response_fragmented_and_truncated },
 	{ "ipc/broken-peer-send", ipc_broken_peer_send },
+	{ "server/connection-ownership", server_connection_ownership },
 	{ "ibus/context-lifecycle", ibus_context_lifecycle },
 };