diff --git a/misc/btpd_if.c b/misc/btpd_if.c
new file mode 100644
index 0000000..8bd0f21
--- /dev/null
+++ b/misc/btpd_if.c
@@ -0,0 +1,313 @@
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+
+#include <assert.h>
+#include <ctype.h>
+#include <err.h>
+#include <errno.h>
+#include <inttypes.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "benc.h"
+#include "btpd_if.h"
+#include "iobuf.h"
+#include "subr.h"
+
+struct ipc {
+    int sd;
+};
+
+static const char *errmsgs[] = {
+#define ERRDEF(name, msg) msg,
+#include "ipcdefs.h"
+#undef ERRDEF
+    NULL
+};
+
+static const char *tval_names[] = {
+#define TVDEF(val, type, name) name,
+#include "ipcdefs.h"
+#undef TVDEF
+    NULL
+};
+
+const char *
+ipc_strerror(enum ipc_err err)
+{
+    if (err < 0 || err >= IPC_ERRCOUNT)
+        return "unknown error";
+    return errmsgs[err];
+}
+
+const char *
+tval_name(enum ipc_tval key)
+{
+    if (key < 0 || key >= IPC_TVALCOUNT)
+        return "unknown key";
+    return tval_names[key];
+}
+
+int
+ipc_open(const char *dir, struct ipc **out)
+{
+    int sd = -1, err = 0;
+    size_t plen;
+    struct ipc *res;
+    struct sockaddr_un addr;
+
+    plen = sizeof(addr.sun_path);
+    if (snprintf(addr.sun_path, plen, "%s/sock", dir) >= plen)
+        return ENAMETOOLONG;
+    addr.sun_family = AF_UNIX;
+
+    if ((sd = socket(PF_UNIX, SOCK_STREAM, 0)) == -1)
+        return errno;
+
+    if (connect(sd, (struct sockaddr *)&addr, sizeof(addr)) == -1) {
+        err = errno;
+        close(sd);
+        return err;
+    }
+
+    if ((res = malloc(sizeof(*res))) == NULL) {
+        close(sd);
+        return ENOMEM;
+    }
+
+    res->sd = sd;
+    *out = res;
+    return 0;
+}
+
+void
+ipc_close(struct ipc *ipc)
+{
+    close(ipc->sd);
+    free(ipc);
+}
+
+static enum ipc_err
+ipc_response(struct ipc *ipc, char **out, uint32_t *len)
+{
+    uint32_t size;
+    char *buf;
+
+    if (read_fully(ipc->sd, &size, sizeof(size)) != 0)
+        return IPC_COMMERR;
+    if (size == 0)
+        return IPC_COMMERR;
+    if ((buf = malloc(size)) == NULL)
+        return IPC_COMMERR;
+    if (read_fully(ipc->sd, buf, size) != 0) {
+        free(buf);
+        return IPC_COMMERR;
+    }
+    *out = buf;
+    *len = size;
+    return IPC_OK;
+}
+
+static enum ipc_err
+ipc_req_res(struct ipc *ipc, const char *req, uint32_t qlen, char **res,
+    uint32_t *rlen)
+{
+    assert(benc_validate(req, qlen) == 0);
+    if (write_fully(ipc->sd, &qlen, sizeof(qlen)) != 0)
+        return IPC_COMMERR;
+    if (write_fully(ipc->sd, req, qlen) != 0)
+        return IPC_COMMERR;
+    if (ipc_response(ipc, res, rlen) != 0)
+        return IPC_COMMERR;
+    if (benc_validate(*res, *rlen) != 0)
+        return IPC_COMMERR;
+    if (!benc_isdct(*res))
+        return IPC_COMMERR;
+    return IPC_OK;
+}
+
+static enum ipc_err
+ipc_buf_req_res(struct ipc *ipc, struct io_buffer *iob, char **res,
+    uint32_t *rlen)
+{
+    enum ipc_err err = ipc_req_res(ipc, iob->buf, iob->buf_off, res, rlen);
+    free(iob->buf);
+    return err;
+}
+
+static enum ipc_err
+ipc_buf_req_code(struct ipc *ipc, struct io_buffer *iob)
+{
+    enum ipc_err err;
+    char *res;
+    uint32_t rlen;
+
+    if ((err = ipc_buf_req_res(ipc, iob, &res, &rlen)) == 0) {
+        err = benc_dget_int(res, "code");
+        free(res);
+    }
+    return err;
+}
+
+enum ipc_err
+btpd_die(struct ipc *ipc, int seconds)
+{
+    struct io_buffer iob;
+    buf_init(&iob, 16);
+    if (seconds >= 0)
+        buf_print(&iob, "l3:diei%dee", seconds);
+    else
+        buf_swrite(&iob, "l3:diee");
+    return ipc_buf_req_code(ipc, &iob);
+}
+
+static enum ipc_err
+tget_common(char *ans, enum ipc_tval *keys, size_t nkeys, tget_cb_t cb,
+    void *arg)
+{
+    int err;
+    const char *res;
+    struct ipc_get_res cbres[IPC_TVALCOUNT];
+
+    if ((err = benc_dget_int(ans, "code")) != 0)
+        return err;
+
+    res = benc_dget_lst(ans, "result");
+    int obji = 0;
+    for (res = benc_first(res); res != NULL; res = benc_next(res)) {
+        if (benc_isint(res)) {
+            cb(obji, benc_int(res, NULL), NULL, arg);
+            obji++;
+            continue;
+        }
+        const char *t = benc_first(res);
+        const char *v = benc_next(t);
+        for (int j = 0; j < nkeys; j++) {
+            cbres[keys[j]].type = benc_int(t, NULL);
+            switch (cbres[keys[j]].type) {
+            case IPC_TYPE_ERR:
+            case IPC_TYPE_NUM:
+                cbres[keys[j]].v.num = benc_int(v, NULL);
+                break;
+            case IPC_TYPE_STR:
+            case IPC_TYPE_BIN:
+                cbres[keys[j]].v.str.p= benc_mem(v, &cbres[keys[j]].v.str.l,
+                    NULL);
+                break;
+            }
+            t = benc_next(v);
+            if (t != NULL)
+                v = benc_next(t);
+        }
+        cb(obji, IPC_OK, cbres, arg);
+        obji++;
+    }
+
+    free(ans);
+    return IPC_OK;
+}
+
+enum ipc_err
+btpd_tget(struct ipc *ipc, struct ipc_torrent *tps, size_t ntps,
+    enum ipc_tval *keys, size_t nkeys, tget_cb_t cb, void *arg)
+{
+    char *res;
+    uint32_t rlen;
+    enum ipc_err err;
+    struct io_buffer iob;
+
+    if (nkeys == 0 || ntps == 0)
+        return IPC_COMMERR;
+
+    buf_init(&iob, 1 << 14);
+    buf_swrite(&iob, "l4:tgetd4:froml");
+    for (int i = 0; i < ntps; i++) {
+        if (tps[i].by_hash) {
+            buf_swrite(&iob, "20:");
+            buf_write(&iob, tps[i].u.hash, 20);
+        } else
+            buf_print(&iob, "i%ue", tps[i].u.num);
+    }
+    buf_swrite(&iob, "e4:keysl");
+    for (int k = 0; k < nkeys; k++)
+        buf_print(&iob, "i%de", keys[k]);
+    buf_swrite(&iob, "eee");
+
+    if ((err = ipc_buf_req_res(ipc, &iob, &res, &rlen)) == 0)
+        err = tget_common(res, keys, nkeys, cb, arg);
+    return err;
+}
+
+enum ipc_err
+btpd_tget_wc(struct ipc *ipc, enum ipc_twc twc, enum ipc_tval *keys,
+    size_t nkeys, tget_cb_t cb, void *arg)
+{
+    char *res;
+    uint32_t rlen;
+    struct io_buffer iob;
+    enum ipc_err err;
+
+    if (nkeys == 0)
+        return IPC_COMMERR;
+
+    buf_init(&iob, 1 << 14);
+    buf_print(&iob, "l4:tgetd4:fromi%de4:keysl", twc);
+    for (int i = 0; i < nkeys; i++)
+        buf_print(&iob, "i%de", keys[i]);
+    buf_swrite(&iob, "eee");
+
+    if ((err = ipc_buf_req_res(ipc, &iob, &res, &rlen)) == 0)
+        err = tget_common(res, keys, nkeys, cb, arg);
+    return err;
+}
+
+enum ipc_err
+btpd_add(struct ipc *ipc, const char *mi, size_t mi_size, const char *content,
+    const char *name)
+{
+    struct io_buffer iob;
+    buf_init(&iob, (1 << 10));
+    buf_print(&iob, "l3:addd7:content%d:%s", (int)strlen(content),
+        content);
+    if (name != NULL)
+        buf_print(&iob, "4:name%d:%s", (int)strlen(name), name);
+    buf_print(&iob, "7:torrent%lu:", (unsigned long)mi_size);
+    buf_write(&iob, mi, mi_size);
+    buf_swrite(&iob, "ee");
+    return ipc_buf_req_code(ipc, &iob);
+}
+
+static enum ipc_err
+simple_treq(struct ipc *ipc, char *cmd, struct ipc_torrent *tp)
+{
+    struct io_buffer iob;
+    buf_init(&iob, 32);
+    if (tp->by_hash) {
+        buf_print(&iob, "l%d:%s20:", (int)strlen(cmd), cmd);
+        buf_write(&iob, tp->u.hash, 20);
+        buf_swrite(&iob, "e");
+    } else
+        buf_print(&iob, "l%d:%si%uee", (int)strlen(cmd), cmd, tp->u.num);
+    return ipc_buf_req_code(ipc, &iob);
+}
+
+enum ipc_err
+btpd_del(struct ipc *ipc, struct ipc_torrent *tp)
+{
+    return simple_treq(ipc, "del", tp);
+}
+
+enum ipc_err
+btpd_start(struct ipc *ipc, struct ipc_torrent *tp)
+{
+    return simple_treq(ipc, "start", tp);
+}
+
+enum ipc_err
+btpd_stop(struct ipc *ipc, struct ipc_torrent *tp)
+{
+    return simple_treq(ipc, "stop", tp);
+}
diff --git a/misc/btpd_if.h b/misc/btpd_if.h
new file mode 100644
index 0000000..ed0d9ba
--- /dev/null
+++ b/misc/btpd_if.h
@@ -0,0 +1,92 @@
+#ifndef BTPD_IPC_H
+#define BTPD_IPC_H
+
+enum ipc_err {
+#define ERRDEF(name, msg) IPC_##name,
+#include "ipcdefs.h"
+#undef ERRDEF
+    IPC_ERRCOUNT
+};
+
+enum ipc_type {
+    IPC_TYPE_ERR,
+    IPC_TYPE_BIN,
+    IPC_TYPE_NUM,
+    IPC_TYPE_STR
+};
+
+enum ipc_tval {
+#define TVDEF(val, type, name) IPC_TVAL_##val,
+#include "ipcdefs.h"
+#undef TVDEF
+    IPC_TVALCOUNT
+};
+
+enum ipc_dval {
+    IPC_DVAL_MIN,
+    IPC_DVAL_MAX
+};
+
+enum ipc_twc {
+    IPC_TWC_ALL,
+    IPC_TWC_ACTIVE,
+    IPC_TWC_INACTIVE
+};
+
+enum ipc_tstate {
+    IPC_TSTATE_INACTIVE,
+    IPC_TSTATE_START,
+    IPC_TSTATE_STOP,
+    IPC_TSTATE_LEECH,
+    IPC_TSTATE_SEED
+};
+
+#ifndef DAEMON
+
+struct ipc;
+
+struct ipc_get_res {
+    enum ipc_type type;
+    union {
+        struct {
+            const char *p;
+            size_t l;
+        } str;
+        long long num;
+    } v;
+};
+
+struct ipc_torrent {
+    int by_hash;
+    union {
+        unsigned num;
+        uint8_t hash[20];
+    } u;
+};
+
+typedef void (*tget_cb_t)(int obji, enum ipc_err objerr,
+    struct ipc_get_res *res, void *arg);
+
+//typedef void (*dget_cb_t)(struct ipc_get_res *res, size_t nres, void *arg);
+
+int ipc_open(const char *dir, struct ipc **out);
+void ipc_close(struct ipc *ipc);
+
+const char *ipc_strerror(enum ipc_err err);
+
+enum ipc_err btpd_add(struct ipc *ipc, const char *mi, size_t mi_size,
+    const char *content, const char *name);
+enum ipc_err btpd_del(struct ipc *ipc, struct ipc_torrent *tp);
+enum ipc_err btpd_start(struct ipc *ipc, struct ipc_torrent *tp);
+enum ipc_err btpd_stop(struct ipc *ipc, struct ipc_torrent *tp);
+enum ipc_err btpd_die(struct ipc *ipc, int seconds);
+enum ipc_err btpd_get(struct ipc *ipc, enum ipc_dval *keys, size_t nkeys,
+    tget_cb_t cb, void *arg);
+enum ipc_err btpd_tget(struct ipc *ipc, struct ipc_torrent *tps, size_t ntps,
+    enum ipc_tval *keys, size_t nkeys, tget_cb_t cb, void *arg);
+enum ipc_err btpd_tget_wc(struct ipc *ipc, enum ipc_twc, enum ipc_tval *keys,
+    size_t nkeys, tget_cb_t cb, void *arg);
+
+#endif
+
+#endif