--- a/packages/net/tcpip/current/src/lib/tftp_server.c
+++ b/packages/net/tcpip/current/src/lib/tftp_server.c
@@ -60,6 +60,32 @@
 #include <cyg/kernel/kapi.h>
 #include <stdlib.h>           // For malloc
 
+#define nCYGOPT_NET_TFTP_SERVER_INSTRUMENT
+#ifdef CYGOPT_NET_TFTP_SERVER_INSTRUMENT
+
+struct subinfo {
+    int rx;
+    int rx_repeat;
+    int rx_skip;
+    int send;
+    int resend;
+};
+
+struct info {
+    struct subinfo ack, data;
+    int err_send;
+    int total_transactions;
+};
+
+
+static struct info tftp_server_instrument = {
+    { 0,0,0,0,0 },
+    { 0,0,0,0,0 },
+    0, 0,
+};
+
+#endif // CYGOPT_NET_TFTP_SERVER_INSTRUMENT
+
 #define STACK_SIZE (CYGNUM_HAL_STACK_SIZE_TYPICAL+(3*(SEGSIZE+sizeof(struct tftphdr))))
 static char *TFTP_tag = "TFTPD";
 struct tftp_server {
@@ -72,16 +98,32 @@ struct tftp_server {
 };
 
 static char * errmsg[] = {
-  "Undefined error code",
-  "File not found",
-  "Access violation",
-  "Disk full or allocation exceeded",
-  "Illegal TFTP operation",
-  "Unknown transfer ID",
-  "File already exists",
-  "No such user" 
+  "Undefined error code",               // 0 nothing defined
+  "File not found",                     // 1 TFTP_ENOTFOUND 
+  "Access violation",                   // 2 TFTP_EACCESS   
+  "Disk full or allocation exceeded",   // 3 TFTP_ENOSPACE  
+  "Illegal TFTP operation",             // 4 TFTP_EBADOP    
+  "Unknown transfer ID",                // 5 TFTP_EBADID    
+  "File already exists",                // 6 TFTP_EEXISTS   
+  "No such user",                       // 7 TFTP_ENOUSER   
 };
 
+/* Send an error packet to the client */
+static void 
+tftpd_send_error(int s, struct tftphdr * reply, int err,
+		 struct sockaddr_in *from_addr, int from_len)
+{
+    CYG_ASSERT( 0 <= err, "err underflow" );
+    CYG_ASSERT( sizeof(errmsg)/sizeof(errmsg[0]) > err, "err overflow" );
+
+    reply->th_opcode = htons(ERROR);
+    reply->th_code = htons(err);
+    if ( (0 > err) || (sizeof(errmsg)/sizeof(errmsg[0]) <= err) )
+        err = 0; // Do not copy a random string from hyperspace
+    strcpy(reply->th_msg, errmsg[err]);
+    sendto(s, reply, 4+strlen(reply->th_msg)+1, 0, 
+	   (struct sockaddr *)from_addr, from_len);
+}
 
 //
 // Receive a file from the client
@@ -95,7 +137,7 @@ tftpd_write_file(struct tftp_server *ser
     char data_in[SEGSIZE+sizeof(struct tftphdr)];
     struct tftphdr *reply = (struct tftphdr *)data_out;
     struct tftphdr *response = (struct tftphdr *)data_in;
-    int fd, block, len, ok, closed, data_len, s;
+    int fd, block, len, ok, tries, closed, data_len, s;
     struct timeval timeout;
     fd_set fds;
     int total_timeouts = 0;
@@ -118,93 +160,113 @@ tftpd_write_file(struct tftp_server *ser
         return;
     }
     if ((fd = (server->ops->open)(hdr->th_stuff, O_WRONLY)) < 0) {
-        reply->th_opcode = htons(ERROR);
-        reply->th_code = htons(TFTP_ENOTFOUND);
-        strcpy(reply->th_msg, errmsg[TFTP_ENOTFOUND]);
-        sendto(s, reply, 4+strlen(reply->th_msg)+1, 0, 
-               (struct sockaddr *)from_addr, from_len);
+        tftpd_send_error(s,reply,TFTP_ENOTFOUND,from_addr, from_len);
         close(s);
         return;
     }
-    // Send ACK telling client he can send data
-    reply->th_opcode = htons(ACK);
-    reply->th_block = 0;
-    sendto(s, reply, 4, 0, (struct sockaddr *)from_addr, from_len);
-    block = 1;
     ok = true;
     closed = false;
+    block = 0;
     while (ok) {
-        timeout.tv_sec = TFTP_TIMEOUT_PERIOD;
-        timeout.tv_usec = 0;
-        FD_ZERO(&fds);
-        FD_SET(s, &fds);
-        if (select(s+1, &fds, 0, 0, &timeout) <= 0) {
-            if (++total_timeouts > TFTP_TIMEOUT_MAX) {
-                ok = false;
-                break;
+        // Send ACK telling client he can send data
+        reply->th_opcode = htons(ACK);
+        reply->th_block = htons(block++); // postincrement
+        for (tries = 0;  tries < TFTP_RETRIES_MAX;  tries++) {
+#ifdef CYGOPT_NET_TFTP_SERVER_INSTRUMENT
+            tftp_server_instrument.ack.send++;
+#endif
+            sendto(s, reply, 4, 0, (struct sockaddr *)from_addr, from_len);
+        repeat_select:
+            timeout.tv_sec = TFTP_TIMEOUT_PERIOD;
+            timeout.tv_usec = 0;
+            FD_ZERO(&fds);
+            FD_SET(s, &fds);
+            if (select(s+1, &fds, 0, 0, &timeout) <= 0) {
+                if (++total_timeouts > TFTP_TIMEOUT_MAX) {
+#ifdef CYGOPT_NET_TFTP_SERVER_INSTRUMENT
+                    tftp_server_instrument.err_send++;
+#endif
+                    tftpd_send_error(s,reply,TFTP_EBADOP,from_addr, from_len);
+                    ok = false;
+                    break;
+                }
+#ifdef CYGOPT_NET_TFTP_SERVER_INSTRUMENT
+                tftp_server_instrument.ack.resend++;
+#endif
+                continue; // retry the send, using up one retry.
             }
-            // Try resending last ACK
-            sendto(s, reply, 4, 0, (struct sockaddr *)from_addr, from_len);
-        } else {
             // Some data has arrived
             data_len = sizeof(data_in);
             client_len = sizeof(client_addr);
             if ((data_len = recvfrom(s, data_in, data_len, 0, 
-                                     (struct sockaddr *)&client_addr, &client_len)) < 0) {
-                // What happened?
-                diag_printf("Can't read client data!\n");
-                ok = false;
+                      (struct sockaddr *)&client_addr, &client_len)) < 0) {
+                // What happened?  No data here!
+#ifdef CYGOPT_NET_TFTP_SERVER_INSTRUMENT
+                tftp_server_instrument.ack.resend++;
+#endif
+                continue; // retry the send, using up one retry.
+            }
+            if (ntohs(response->th_opcode) == DATA &&
+                ntohs(response->th_block) < block) {
+#ifdef CYGOPT_NET_TFTP_SERVER_INSTRUMENT
+                tftp_server_instrument.data.rx_repeat++;
+#endif
+                // Then it is repeat DATA with an old block; listen again,
+                // but do not repeat sending the current ack, and do not
+                // use up a retry count.  (we do re-send the ack if
+                // subsequently we time out)
+                goto repeat_select;
+            }
+            if (ntohs(response->th_opcode) == DATA &&
+                ntohs(response->th_block) == block) {
+#ifdef CYGOPT_NET_TFTP_SERVER_INSTRUMENT
+                tftp_server_instrument.data.rx++;
+#endif
+                // Good data - write to file
+                len = (server->ops->write)(fd, response->th_data, data_len-4);
+                if (len < (data_len-4)) {
+                    // File is "full"
+                    tftpd_send_error(s,reply,TFTP_ENOSPACE,
+                                     from_addr, from_len);     
+                    ok = false;  // Give up
+                    break; // out of the retries loop
+                }
+                if (data_len < (SEGSIZE+4)) {
+                    // End of file
+                    closed = true;
+                    ok = false;
+                    if ((server->ops->close)(fd) == -1) {
+                        tftpd_send_error(s,reply,TFTP_EACCESS,
+                                         from_addr, from_len);
+                        break;  // out of the retries loop
+                    }
+                    // Exception to the loop structure: we must ACK the last
+                    // packet, the one that implied EOF:
+#ifdef CYGOPT_NET_TFTP_SERVER_INSTRUMENT
+                    tftp_server_instrument.ack.send++;
+#endif
+                    reply->th_opcode = htons(ACK);
+                    reply->th_block = htons(block++); // postincrement
+                    sendto(s, reply, 4, 0, (struct sockaddr *)from_addr, from_len);
+                    break; // out of the retries loop
+                }
+                // Happy!  Break out of the retries loop.
                 break;
             }
-            if (ntohs(response->th_opcode) == DATA) {
-                if (ntohs(response->th_block) == block) {
-                    // Good data - write to file
-                    len = (server->ops->write)(fd, response->th_data, data_len-4);
-                    if (len < (data_len-4)) {
-                        // File is "full"
-                        reply->th_opcode = htons(ERROR);
-                        reply->th_code = htons(TFTP_ENOSPACE);
-                        strcpy(reply->th_msg, errmsg[TFTP_ENOSPACE]);
-                        sendto(s, reply, 4+strlen(reply->th_msg)+1, 0, 
-                               (struct sockaddr *)from_addr, from_len);
-                        ok = false;  // Give up
-                    } else {
-                        if (data_len < (SEGSIZE+4)) {
-                            // End of file
-                            closed = true;
-                            ok = false;
-                            if ((server->ops->close)(fd) == -1) {
-                                reply->th_opcode = htons(ERROR);
-                                reply->th_code = htons(TFTP_EACCESS); 
-                                strcpy(reply->th_msg, errmsg[TFTP_EACCESS]);
-                                sendto(s, reply, 4+strlen(reply->th_msg)+1, 0, 
-                                    (struct sockaddr *)from_addr, from_len);
-                            } else {
-                                reply->th_opcode = htons(ACK);
-                                reply->th_block = htons(block++);
-                                sendto(s, reply, 4, 0,
-                                       (struct sockaddr *)from_addr, from_len);
-                            }
-                        } else {
-                            reply->th_opcode = htons(ACK);
-                            reply->th_block = htons(block++);
-                            sendto(s, reply, 4, 0,
-                                   (struct sockaddr *)from_addr, from_len);
-                        }
-                    }
-                } else {
-                    // Something is wrong - tell client last good block
-                    sendto(s, reply, 4, 0, (struct sockaddr *)from_addr, from_len);
-                }
-            } else {
-                // Client has sent something bogus - bag out!
-                reply->th_opcode = htons(ERROR);
-                reply->th_code = htons(TFTP_EBADOP); 
-                strcpy(reply->th_msg, errmsg[TFTP_EBADOP]);
-                sendto(s, reply, 4+strlen(reply->th_msg)+1, 0, 
-                       (struct sockaddr *)from_addr, from_len);
-                ok = false;
-            }
+            // Otherwise, we got something we do not understand!  So repeat
+            // sending the current ACK, and use up a retry count.
+#ifdef CYGOPT_NET_TFTP_SERVER_INSTRUMENT
+            if ( (ntohs(response->th_opcode) == DATA) )
+                tftp_server_instrument.data.rx_skip++;
+            tftp_server_instrument.ack.resend++;
+#endif
+        } // End of the retries loop.
+        if (TFTP_RETRIES_MAX <= tries) {
+#ifdef CYGOPT_NET_TFTP_SERVER_INSTRUMENT
+            tftp_server_instrument.err_send++;
+#endif
+            tftpd_send_error(s,reply,TFTP_EBADOP,from_addr, from_len);
+            ok = false;
         }
     }
     close(s);
@@ -248,11 +310,7 @@ tftpd_read_file(struct tftp_server *serv
         return;
     }
     if ((fd = (server->ops->open)(hdr->th_stuff, O_RDONLY)) < 0) {
-        reply->th_opcode = htons(ERROR);
-        reply->th_code = htons(TFTP_ENOTFOUND);
-        strcpy(reply->th_msg, errmsg[TFTP_ENOTFOUND]);
-        sendto(s, reply, 4+strlen(reply->th_msg)+1, 0, 
-               (struct sockaddr *)from_addr, from_len);
+        tftpd_send_error(s,reply,TFTP_ENOTFOUND,from_addr, from_len);
         close(s);
         return;
     }
@@ -261,10 +319,14 @@ tftpd_read_file(struct tftp_server *serv
     while (ok) {
         // Read next chunk of file
         len = (server->ops->read)(fd, reply->th_data, SEGSIZE);
-        reply->th_block = htons(++block);
+        reply->th_block = htons(++block); // preincrement
         reply->th_opcode = htons(DATA);
         for (tries = 0;  tries < TFTP_RETRIES_MAX;  tries++) {
-            if (sendto(s, reply, 4+len, 0, (struct sockaddr *)from_addr, from_len) < 0) {
+#ifdef CYGOPT_NET_TFTP_SERVER_INSTRUMENT
+            tftp_server_instrument.data.send++;
+#endif
+            if (sendto(s, reply, 4+len, 0,
+                       (struct sockaddr *)from_addr, from_len) < 0) {
                 // Something went wrong with the network!
                 ok = false;
                 break;
@@ -276,9 +338,16 @@ tftpd_read_file(struct tftp_server *serv
             FD_SET(s, &fds);
             if (select(s+1, &fds, 0, 0, &timeout) <= 0) {
                 if (++total_timeouts > TFTP_TIMEOUT_MAX) {
+#ifdef CYGOPT_NET_TFTP_SERVER_INSTRUMENT
+                    tftp_server_instrument.err_send++;
+#endif
+ 		    tftpd_send_error(s,reply,TFTP_EBADOP,from_addr, from_len);
                     ok = false;
                     break;
                 }
+#ifdef CYGOPT_NET_TFTP_SERVER_INSTRUMENT
+                tftp_server_instrument.data.resend++;
+#endif
                 continue; // retry the send, using up one retry.
             }
             data_len = sizeof(data_in);
@@ -287,23 +356,47 @@ tftpd_read_file(struct tftp_server *serv
                                      (struct sockaddr *)&client_addr,
                                      &client_len)) < 0) {
                 // What happened?  Maybe someone lied to us...
+#ifdef CYGOPT_NET_TFTP_SERVER_INSTRUMENT
+                tftp_server_instrument.data.resend++;
+#endif
                 continue; // retry the send, using up one retry.
             }
             if ((ntohs(response->th_opcode) == ACK) &&
                 (ntohs(response->th_block) < block)) {
+#ifdef CYGOPT_NET_TFTP_SERVER_INSTRUMENT
+                tftp_server_instrument.ack.rx_repeat++;
+#endif
                 // Then it is a repeat ACK for an old block; listen again,
                 // but do not repeat sending the current block, and do not
-                // use up a retry count.
+                // use up a retry count.  (we do re-send the data if
+                // subsequently we time out)
                 goto repeat_select;
             }
             if ((ntohs(response->th_opcode) == ACK) &&
                 (ntohs(response->th_block) == block)) {
+#ifdef CYGOPT_NET_TFTP_SERVER_INSTRUMENT
+                tftp_server_instrument.ack.rx++;
+#endif
                 // Happy!  Break out of the retries loop.
                 break;
             }
+            // Otherwise, we got something we do not understand!  So repeat
+            // sending the current block, and use up a retry count.
+#ifdef CYGOPT_NET_TFTP_SERVER_INSTRUMENT
+            if ( (ntohs(response->th_opcode) == ACK) )
+                tftp_server_instrument.ack.rx_skip++;
+            tftp_server_instrument.data.resend++;
+#endif
+        } // End of the retries loop.
+        if (TFTP_RETRIES_MAX <= tries) {
+#ifdef CYGOPT_NET_TFTP_SERVER_INSTRUMENT
+            tftp_server_instrument.err_send++;
+#endif
+            tftpd_send_error(s,reply,TFTP_EBADOP,from_addr, from_len);
+            ok = false;
         }
         if (len < SEGSIZE) {
-            break;
+            break; // That's end of file then.
         }
     }
     close(s);
@@ -313,6 +406,11 @@ tftpd_read_file(struct tftp_server *serv
 //
 // Actual TFTP server
 //
+#define CYGSEM_TFTP_SERVER_MULTITHREADED
+#ifdef CYGSEM_TFTP_SERVER_MULTITHREADED
+static cyg_sem_t tftp_server_sem;
+#endif
+
 static void
 tftpd_server(cyg_addrword_t p)
 {
@@ -326,7 +424,7 @@ tftpd_server(cyg_addrword_t p)
 
 #ifndef CYGPKG_NET_TESTS_USE_RT_TEST_HARNESS
     // Otherwise routine printfs fail the test - interrupts disabled too long.
-    diag_printf("TFTPD: %x, port: %d\n", p, server->port);
+    diag_printf("TFTPD [%x]: port %d\n", p, server->port);
 #endif
 
     // Set up port
@@ -339,33 +437,53 @@ tftpd_server(cyg_addrword_t p)
         server->port = server_info->s_port;
     }
 
-    // Create socket
-    s = socket(AF_INET, SOCK_DGRAM, 0);
-    if (s < 0) {
-        diag_printf("TFTPD: can't open socket\n");
-        return;
-    }
-    memset((char *)&local_addr, 0, sizeof(local_addr));
-    local_addr.sin_family = AF_INET;
-    local_addr.sin_addr.s_addr = htonl(INADDR_ANY);
-    local_addr.sin_port = htons(server->port);
-    if (bind(s, (struct sockaddr *)&local_addr, sizeof(local_addr)) < 0) {
-        // Problem setting up my end
-        diag_printf("TFTPD: can't bind to service port\n");
-        close(s);
-        return;
-    }
+    while (true) {
+#ifdef CYGOPT_NET_TFTP_SERVER_INSTRUMENT
+        struct info o = tftp_server_instrument;
+#endif
+        // Create socket
+        s = socket(AF_INET, SOCK_DGRAM, 0);
+        if (s < 0) {
+            diag_printf("TFTPD [%x]: can't open socket\n", p);
+            return;
+        }
+        memset((char *)&local_addr, 0, sizeof(local_addr));
+        local_addr.sin_family = AF_INET;
+        local_addr.sin_addr.s_addr = htonl(INADDR_ANY);
+        local_addr.sin_port = htons(server->port);
+        if (bind(s, (struct sockaddr *)&local_addr, sizeof(local_addr)) < 0) {
+            // Problem setting up my end
+            close(s);
+#ifdef CYGSEM_TFTP_SERVER_MULTITHREADED
+#ifndef CYGPKG_NET_TESTS_USE_RT_TEST_HARNESS
+            diag_printf("TFTPD [%x]: waiting to bind to service port\n", p);
+#endif
+            // Wait until the socket is free...
+            cyg_semaphore_wait( &tftp_server_sem );
+            continue; // try re-opening and rebinding the socket.
+#else
+            diag_printf("TFTPD [%x]: can't bind to service port\n", p);
+            return;
+#endif
+        }
 
-    while (true) {
         recv_len = sizeof(data);
         from_len = sizeof(from_addr);
-        if ((data_len = recvfrom(s, hdr, recv_len, 0, 
-                                 (struct sockaddr *)&from_addr, &from_len)) < 0) {
-            diag_printf("TFTPD: can't read request\n");
+        data_len = recvfrom(s, hdr, recv_len, 0,
+                            (struct sockaddr *)&from_addr, &from_len);
+        close(s); // so that other servers can bind to the TFTP socket
+#ifdef CYGSEM_TFTP_SERVER_MULTITHREADED
+        // The socket is free...
+        cyg_semaphore_post( &tftp_server_sem );
+#endif
+
+        if ( data_len < 0) {
+            diag_printf("TFTPD [%x]: can't read request\n", p);
         } else {
 #ifndef CYGPKG_NET_TESTS_USE_RT_TEST_HARNESS
-            diag_printf("TFTPD: received %x from %s:%d\n", 
-                        ntohs(hdr->th_opcode), inet_ntoa(from_addr.sin_addr), from_addr.sin_port);
+            diag_printf("TFTPD [%x]: received %x from %s:%d\n", p,
+                        ntohs(hdr->th_opcode), inet_ntoa(from_addr.sin_addr),
+                        from_addr.sin_port);
 #endif
             switch (ntohs(hdr->th_opcode)) {
             case WRQ:
@@ -380,15 +498,46 @@ tftpd_server(cyg_addrword_t p)
                 // Ignore
                 break;
             default:
-                diag_printf("TFTPD: bogus request %x from %s:%d\n", 
-                            ntohs(hdr->th_opcode), inet_ntoa(from_addr.sin_addr), from_addr.sin_port);
-                hdr->th_opcode = htons(ERROR);
-                hdr->th_code = htons(TFTP_EBADOP);
-                strcpy(hdr->th_msg, errmsg[TFTP_EBADOP]);;
-                sendto(s, hdr, 4+strlen(hdr->th_msg)+1, 0, 
-                       (struct sockaddr *)&from_addr, from_len);
+                diag_printf("TFTPD [%x]: bogus request %x from %s:%d\n", p,
+                            ntohs(hdr->th_opcode),
+                            inet_ntoa(from_addr.sin_addr),
+                            from_addr.sin_port );
+                tftpd_send_error(s,hdr,TFTP_EBADOP,&from_addr,from_len);
             }
         }
+#ifdef CYGOPT_NET_TFTP_SERVER_INSTRUMENT
+        tftp_server_instrument.total_transactions++;
+
+        o.data.rx        -= tftp_server_instrument.data.rx       ;
+        o.data.rx_repeat -= tftp_server_instrument.data.rx_repeat;
+        o.data.rx_skip   -= tftp_server_instrument.data.rx_skip  ;
+        o.data.send      -= tftp_server_instrument.data.send     ;
+        o.data.resend    -= tftp_server_instrument.data.resend   ;
+
+        o.ack.rx         -= tftp_server_instrument.ack.rx        ;
+        o.ack.rx_repeat  -= tftp_server_instrument.ack.rx_repeat ;
+        o.ack.rx_skip    -= tftp_server_instrument.ack.rx_skip   ;
+        o.ack.send       -= tftp_server_instrument.ack.send      ;
+        o.ack.resend     -= tftp_server_instrument.ack.resend    ;
+
+        o.err_send       -= tftp_server_instrument.err_send      ;
+
+#ifndef CYGPKG_NET_TESTS_USE_RT_TEST_HARNESS
+        if ( o.data.rx        ) diag_printf( "data rx       %4d\n", -o.data.rx        );
+        if ( o.data.rx_repeat ) diag_printf( "data rx_repeat%4d\n", -o.data.rx_repeat );
+        if ( o.data.rx_skip   ) diag_printf( "data rx_skip  %4d\n", -o.data.rx_skip   );
+        if ( o.data.send      ) diag_printf( "data send     %4d\n", -o.data.send      );
+        if ( o.data.resend    ) diag_printf( "data resend   %4d\n", -o.data.resend    );
+
+        if ( o.ack.rx        ) diag_printf( " ack rx       %4d\n", -o.ack.rx        );
+        if ( o.ack.rx_repeat ) diag_printf( " ack rx_repeat%4d\n", -o.ack.rx_repeat );
+        if ( o.ack.rx_skip   ) diag_printf( " ack rx_skip  %4d\n", -o.ack.rx_skip   );
+        if ( o.ack.send      ) diag_printf( " ack send     %4d\n", -o.ack.send      );
+        if ( o.ack.resend    ) diag_printf( " ack resend   %4d\n", -o.ack.resend    );
+
+        if ( o.err_send      ) diag_printf( "*error sends  %4d\n", -o.err_send      );
+#endif // CYGPKG_NET_TESTS_USE_RT_TEST_HARNESS
+#endif // CYGOPT_NET_TFTP_SERVER_INSTRUMENT
     }
 }
 
@@ -405,6 +554,14 @@ int
 tftpd_start(int port, struct tftpd_fileops *ops)
 {
     struct tftp_server *server;
+#ifdef CYGSEM_TFTP_SERVER_MULTITHREADED
+    static char init = 0;
+    if ( 0 == init ) {
+        init++;
+        cyg_semaphore_init( &tftp_server_sem, 0 );
+    }
+#endif
+
     if ((server = malloc(sizeof(struct tftp_server)))) {
         server->tag = TFTP_tag;
         server->port = port;