added check to prevent yarp read stealing ports already in use

doc/release/master/safe_yarpread.md

@@ -0,0 +1,9 @@
+safe-yarpread {#master}
+---------------------------------
+
+New Features
+------------
+
+### lib_yarp_companion
+
+* commands 'yarp read' and 'yarp write' now checks that target ports do not already exist.

src/libYARP_companion/src/yarp/companion/impl/Companion.cmdRead.cpp

@@ -8,6 +8,7 @@
 #include <yarp/companion/impl/BottleReader.h>
 #include <yarp/os/ContactStyle.h>
 #include <yarp/os/Network.h>
+#include <yarp/os/LogStream.h>
 
 #include <cstring>
 
@@ -77,5 +78,14 @@ int Companion::cmdRead(int argc, char *argv[])
         argc--;
         argv++;
     }
+
+    //the following check prevents opening as local port a port which is already registered (and active) on the yarp nameserver
+    bool e = NetworkBase::exists(name, true);
+    if (e)
+    {
+        yCError(COMPANION) << "Port"<< name << "already exists! Do you mean yarp read ..."<< name <<"?";
+        return 1;
+    }
+
     return read(name, src, showEnvelope, trim);
 }

src/libYARP_companion/src/yarp/companion/impl/Companion.cmdWrite.cpp

@@ -9,6 +9,8 @@
 #include <yarp/os/Port.h>
 #include <yarp/os/SystemClock.h>
 #include <yarp/os/impl/Terminal.h>
+#include <yarp/os/Network.h>
+#include <yarp/os/LogStream.h>
 
 #ifdef YARP_HAS_Libedit
 #include <yarp/conf/dirs.h>
@@ -24,6 +26,7 @@ using yarp::companion::impl::Companion;
 using yarp::os::Bottle;
 using yarp::os::Port;
 using yarp::os::SystemClock;
+using yarp::os::NetworkBase;
 
 int Companion::write(const char *name, int ntargets, char *targets[]) {
     Port port;
@@ -154,5 +157,14 @@ int Companion::cmdWrite(int argc, char *argv[])
     }
 
     const char *src = argv[0];
+
+    //the following check prevents opening as local port a port which is already registered (and active) on the yarp nameserver
+    bool e = NetworkBase::exists(src, true);
+    if (e)
+    {
+        yCError(COMPANION) << "Port" << src << "already exists! Aborting...";
+        return 1;
+    }
+
     return write(src, argc-1, argv+1);
 }