我首先要说我是一名几乎没有 c++ 经验的大学生。你听过多少次是对的？我正在使用 libnodave 库中的测试程序 testISO_TCP（简化版）。该程序在连接到 seimens 300 PLC 时对标志值和数据块进行简单读取。该程序本身不会产生任何错误。我想要做的是希望在这个程序中添加一些代码，以保护读取不会崩溃。让我解释得更好一点。例如，我在代码中实现了很多读取。到目前为止，只有两个读取。最终，我将通过更多读取来运行此代码。现在，假设我正在运行测试程序，但由于某种原因我失去了与 PLC 的连接。我想让程序做两件事之一：1）一旦连接丢失，进行一定次数的重试连接，当尝试次数用完时，退出。或 2) 不知何故继续从 PLC 读取，直到它们全部完成。
我希望这是足够的信息来获得一些帮助。我将发布我长期以来一直在寻找的代码，但不知道如何有效地做到这一点。提前感谢大家。
#define PLAY_WITH_KEEPALIVE
#include <stdlib.h>
#include <stdio.h>
#include "nodavesimple.h"
#include "openSocket.h"
#ifdef PLAY_WITH_KEEPALIVE
#include <winsock.h>
#endif
int main(int argc, char **argv) {
int a,b,c,res, doRun, doStop, doRead, doreadFlag, useProtocol, useSlot;
#ifdef PLAY_WITH_KEEPALIVE
int opt;
#endif
float d;
daveInterface * di;
daveConnection * dc;
_daveOSserialType fds;
doRun=0;
doStop=0;
doRead=0;
doreadFlag=0;
useProtocol=daveProtoISOTCP;
useSlot=2;
fds.rfd=openSocket(102, argv[1]);
#ifdef PLAY_WITH_KEEPALIVE
errno=0;
opt=1;
//res=setsockopt(fds.rfd, SOL_SOCKET, SO_KEEPALIVE, &opt, 4);
//LOG3("setsockopt %s %d\n", strerror(errno),res);
#endif
fds.wfd=fds.rfd;
if (fds.rfd>0)
{
di =daveNewInterface(fds,"IF1",0, daveProtoISOTCP, daveSpeed187k);
daveSetTimeout(di,5000000);
dc =daveNewConnection(di,2,0, 2); // insert your rack and slot here
if (0==daveConnectPLC(dc))
{
printf("Connected.\n");
res=daveReadBytes(dc,daveFlags,0,0,16,NULL);
if (0==res)
{
a=daveGetU32(dc);
b=daveGetU32(dc);
c=daveGetU32(dc);
d=daveGetFloat(dc);
printf("FD0: %d\n",a);
printf("FD4: %d\n",b);
printf("FD8: %d\n",c);
printf("FD12: %f\n",d);
}//end 0==res
}//end daveConnectPLC
else
{
printf("Couldn't connect to PLC.\n Please make sure you use the -2 option with a CP243 but not with CPs 343 or 443.\n");
//closeSocket(fds.rfd);
//return -2;
}
}//end fds.rfd
fds.rfd=openSocket(102, argv[1]);
fds.wfd=fds.rfd;
if (fds.rfd>0)
{
di =daveNewInterface(fds,"IF1",0, daveProtoISOTCP, daveSpeed187k);
daveSetTimeout(di,5000000);
dc =daveNewConnection(di,2,0, 2); // insert your rack and slot here
if (0==daveConnectPLC(dc))
{
printf("Connected.\n");
res=daveReadBytes(dc,daveDB,1,0,64,NULL);
if (0==res)
{
a=daveGetU16(dc);
printf("DB1:DW0: %d\n",a);
a=daveGetU16(dc);
printf("DB1:DW1: %d\n...\n",a);
a=daveGetU16At(dc,62);
printf("DB1:DW32: %d\n",a);
}//end 0==res
return 0;
}//end daveConnectPLC
else
{
printf("Couldn't connect to PLC.\n Please make sure you use the -2 option with a CP243 but not with CPs 343 or 443.\n");
closeSocket(fds.rfd);
return -2;
}
}//end fds.rfd
else
{
printf("Couldn't open TCP port. \nPlease make sure a CP is connected and the IP address is ok. \n");
return -1;
}
}// end main