TCP time-apps.

* IPv4 instead of IPv6.
* Reliable send/recv.

prrt/time-protocol.h

-
 #include <assert.h>
 
 #ifdef XLAP
@@ -12,6 +11,7 @@
 #  include <sys/socket.h>
 #  include <netdb.h>
 #  include <unistd.h>
+#  include <netinet/in.h>
 
 typedef int socket_t;
 
@@ -45,17 +45,18 @@ static inline socket_t _open_sender(struct arguments *args)
 
 static inline socket_t _open_receiver(struct arguments *args)
 {
-    int ssock = socket(AF_INET6, SOCK_STREAM, 0);
+    int ssock = socket(AF_INET, SOCK_STREAM, 0);
     assert(ssock >= 0);
 
     int yes = 1;
     setsockopt(ssock, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(yes));
 
-    struct sockaddr_in6 address = {
-        .sin6_family = AF_INET6,
-        .sin6_port = htons(args->port),
-        .sin6_addr = in6addr_any,
+    struct sockaddr_in address = {
+        .sin_family = AF_INET,
+        .sin_port = htons(args->port),
     };
+    memset(address.sin_zero, '\0', sizeof(address.sin_zero));
+    address.sin_addr.s_addr = htonl(INADDR_ANY);
     assert(0 == bind(ssock, (const struct sockaddr *) &address, sizeof(address)));
 
     assert(0 == listen(ssock, SOMAXCONN));
@@ -70,12 +71,28 @@ static inline socket_t _open_receiver(struct arguments *args)
 
 static inline void _send(socket_t conn, const char *buf, size_t size)
 {
-    write(conn, buf, size);
+    int written = 0;
+    int n = 0;
+    while (written < size) {
+        n = send(conn, buf, size, 0);
+        written += n;
+        buf += n;
+    }
 }
 
 static inline ssize_t _recv(socket_t conn, char *buf, size_t size)
 {
-    return read(conn, buf, size);
+    ssize_t received = 0;
+    int n = 0;
+    while (received < size) {
+        n = recv(conn, buf, size - received, 0);
+        if (n == 0) {
+            break;
+        }
+        buf += n;
+        received += n;
+    }
+    return received;
 }
 
 static inline void _close(socket_t conn)