diff --git a/trunk/.gitignore b/trunk/.gitignore
index 1cbd7b7e6..a59009bab 100644
--- a/trunk/.gitignore
+++ b/trunk/.gitignore
@@ -45,7 +45,6 @@ srs
 /janus
 *.dump
 bug
-/research/thread-model/thread-local
 *.gcp
 *.svg
 
diff --git a/trunk/research/thread-model/.gitignore b/trunk/research/thread-model/.gitignore
new file mode 100644
index 000000000..1abd1fc86
--- /dev/null
+++ b/trunk/research/thread-model/.gitignore
@@ -0,0 +1,3 @@
+thread-local
+udp-connect-client
+udp-connect-server
diff --git a/trunk/research/thread-model/udp-connect-client.cpp b/trunk/research/thread-model/udp-connect-client.cpp
new file mode 100644
index 000000000..dd16c6125
--- /dev/null
+++ b/trunk/research/thread-model/udp-connect-client.cpp
@@ -0,0 +1,63 @@
+/*
+g++ udp-connect-client.cpp ../../objs/st/libst.a -g -O0 -o udp-connect-client &&
+./udp-connect-client 127.0.0.1 8000 1
+*/
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+#include "../../objs/st/st.h"
+
+#include <sys/socket.h>
+#include <arpa/inet.h>
+
+void* pfn(void* arg) {
+    sockaddr_in addr = *(sockaddr_in*)arg;
+    char* ip = inet_ntoa(addr.sin_addr);
+    int port = ntohs(addr.sin_port);
+
+    int fd = ::socket(AF_INET, SOCK_DGRAM, 0);
+    st_netfd_t stfd = st_netfd_open_socket(fd);
+    printf("connect to %s:%d, fd=%d ok\n", ip, port, fd);
+
+    while (true) {
+        char data[] = "Hello world!";
+        int r0 = st_sendto(stfd, data, sizeof(data), (sockaddr*)&addr, sizeof(sockaddr_in), ST_UTIME_NO_TIMEOUT);
+        printf("fd #%d, send %dB %s, r0=%d\n", fd, (int)sizeof(data), data, r0);
+        if (r0 != (int)sizeof(data)) {
+            break;
+        }
+        st_usleep(800 * 1000);
+    }
+
+    st_netfd_close(stfd);
+
+    return NULL;
+}
+
+int main(int argc, char** argv) {
+    if (argc < 4) {
+        printf("Usage: %s ip port workers\n", argv[0]);
+        exit(-1);
+    }
+
+    st_init();
+
+    const char* ip = argv[1];
+    int port = ::atoi(argv[2]);
+    int workers = ::atoi(argv[3]);
+    printf("Start %d workers, to %s:%d\n", workers, ip, port);
+
+    sockaddr_in addr;
+    addr.sin_family = AF_INET;
+    addr.sin_addr.s_addr = inet_addr(ip);
+    addr.sin_port = htons(port);
+
+    for (int i = 0; i < workers; i++) {
+        st_thread_t thread = st_thread_create(pfn, &addr, 1, 0);
+        assert(thread);
+    }
+
+    st_thread_exit(NULL);
+    return 0;
+}
+
diff --git a/trunk/research/thread-model/udp-connect-server.cpp b/trunk/research/thread-model/udp-connect-server.cpp
new file mode 100644
index 000000000..32f0901d3
--- /dev/null
+++ b/trunk/research/thread-model/udp-connect-server.cpp
@@ -0,0 +1,110 @@
+/*
+g++ udp-connect-server.cpp ../../objs/st/libst.a -g -O0 -o udp-connect-server &&
+./udp-connect-server 127.0.0.1 8000 2
+*/
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+#include "../../objs/st/st.h"
+
+#include <sys/socket.h>
+#include <arpa/inet.h>
+
+#include <vector>
+using namespace std;
+
+vector<int> lfds;
+
+void* pfn(void* arg) {
+    sockaddr_in addr = *(sockaddr_in*)arg;
+    char* ip = inet_ntoa(addr.sin_addr);
+    int port = ntohs(addr.sin_port);
+
+    int fd = ::socket(AF_INET, SOCK_DGRAM, 0);
+    assert(fd > 0);
+
+    lfds.push_back(fd);
+
+    // Find another thread to recv packet.
+    int migrate_fd = 0;
+    while (!migrate_fd) {
+        for (int i = 0; i < (int)lfds.size(); i++) {
+            if (lfds.at(i) != fd) {
+                migrate_fd = lfds.at(i);
+                break;
+            }
+        }
+        st_usleep(10 * 1000);
+    }
+
+    if (true) {
+        int v = 1;
+        int r0 = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &v, sizeof(int));
+        assert(r0 != -1);
+    }
+    if (true) {
+        int v = 1;
+        int r0 = setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &v, sizeof(int));
+        assert(r0 != -1);
+    }
+    if (true) {
+        int r0 = bind(fd, (sockaddr*)&addr, sizeof(sockaddr_in));
+        assert(!r0);
+    }
+
+    st_netfd_t stfd = st_netfd_open_socket(fd);
+    printf("listen at %s:%d, fd=%d, migrate_fd=%d ok\n", ip, port, fd, migrate_fd);
+
+    while (true) {
+        char buf[1600] = {0};
+        sockaddr_in from;
+        int nb_from = sizeof(from);
+        int r0 = st_recvfrom(stfd, buf, sizeof(buf), (sockaddr*)&from, &nb_from, ST_UTIME_NO_TIMEOUT);
+        printf("fd #%d, peer %s:%d, got %dB, %s\n", fd, inet_ntoa(from.sin_addr), ntohs(from.sin_port), r0, buf);
+        if (r0 <= 0) {
+            break;
+        }
+
+        // When we got the packet, connect to another thread.
+        // If it is of type SOCK_DGRAM, this call specifies the peer with which the socket
+        // is to be associated; this address is that to which datagrams are to be sent, and
+        // the only address from which datagrams are to be received.
+        errno = 0;
+        r0 = connect(migrate_fd, (const sockaddr*)&from, (socklen_t)nb_from);
+        printf("Transfer %s:%d from #%d to #%d, r0=%d, errno=%d\n", inet_ntoa(from.sin_addr), ntohs(from.sin_port),
+            fd, migrate_fd, r0, errno);
+
+        st_usleep(10 * 1000);
+    }
+
+    st_netfd_close(stfd);
+    return NULL;
+}
+
+int main(int argc, char** argv) {
+    if (argc < 4) {
+        printf("Usage: %s ip port workers\n", argv[0]);
+        exit(-1);
+    }
+
+    st_init();
+
+    const char* ip = argv[1];
+    int port = ::atoi(argv[2]);
+    int workers = ::atoi(argv[3]);
+    printf("Start %d workers, at %s:%d\n", workers, ip, port);
+
+    sockaddr_in addr;
+    addr.sin_family = AF_INET;
+    addr.sin_addr.s_addr = inet_addr(ip);
+    addr.sin_port = htons(port);
+
+    for (int i = 0; i < workers; i++) {
+        st_thread_t thread = st_thread_create(pfn, &addr, 1, 0);
+        assert(thread);
+    }
+
+    st_thread_exit(NULL);
+    return 0;
+}
+