vpcd: add TCP_NODELAY socket option

Idea from @jetfire13

closes https://github.com/frankmorgner/vsmartcard/pull/323

(cherry picked from commit 92d918e56d25c7c29dabbcac030a30655aeaa3a1)

virtualsmartcard/src/vpcd/vpcd.c

@@ -39,6 +39,7 @@ typedef WORD uint16_t;
 #include <arpa/inet.h>
 #include <netdb.h>
 #include <netinet/in.h>
+#include <netinet/tcp.h> /* for TCP_NODELAY */
 #include <poll.h>
 #include <stdint.h>
 #include <sys/socket.h>
@@ -47,6 +48,7 @@ typedef WORD uint16_t;
 #define INVALID_SOCKET -1
 #endif
 
+
 #include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -110,6 +112,10 @@ static SOCKET opensock(unsigned short port)
     if (setsockopt(sock, SOL_SOCKET, SO_NOSIGPIPE, (void *) &yes, sizeof yes) != 0)
         goto err;
 #endif
+#ifdef TCP_NODELAY
+    if(setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, (void *) &yes, sizeof yes) != 0)
+        goto err;
+#endif
 
     memset(&server_sockaddr, 0, sizeof server_sockaddr);
     server_sockaddr.sin_family      = PF_INET;