Hi Noam, I did not expect any replies, but you did. I appreciate your suggestions.
I am using Socket using Lwip and do not have any issues to handle semaphore, mutex, etc.. to manage tasks/threads using FreeRTOS. So, I think I can apply this skills to others. I am working on embedded development using micro controller but I know xml and a little of HTML, not Java scripts and JSON. Vancouver, Canada area where I live in has a few opportunities for doing that. There are more opportunities for only software side like Linux Kernel, so as for electrical/electronics guy like me it is hard to get into that side. Again, I really appreciate your suggestions. Regards, Jin On Thu, Jun 23, 2016 at 8:01 AM, Noam Weissman <[email protected]> wrote: > Hi, > > > > LwIP and FreeRTOS are popular because they are open source and free. > > > > If you understand how an OS works and have background in TCP/IP you should > > not have a problem learning other TCP stack’s and/or other OS. > > > > Finding a job is not only finding to work with something you are familiar > with but > > more than that. It is adapting/learning other systems and other tools. > > > > If you only worked with LwIP RAW mode then I encourage you to learn some > Socket > > programing as this is much more common. > > > > Most RT OS are similar, meaning they use semaphores, create tasks/threads, > using queue’s etc… > > > > If you are looking for a job, use the time in between to learn new skills. > Learn some JS, XML, > > JSON, HTML etc… > > > > > > Good luck, > > Noam. > > *From:* lwip-users [mailto:[email protected]] *On > Behalf Of *Jin Won Seo > *Sent:* Thursday, June 23, 2016 5:42 PM > *To:* Mailing list for lwIP users > *Subject:* Re: [lwip-users] LwIP multithread select mode problems > > > > Sorry for irrelevant reply, but I am so frustrated to find a job. > > I used Lwip 1.4.1 in my project + RTOS, but ... almost nothing I can find. > > Is this industry dead? These skill sets are not useful? > > > > On Thu, Jun 23, 2016 at 7:33 AM, Joel Cunningham <[email protected]> > wrote: > > Hi, > > > > select() can be used by multiple threads at the same time and you can even > have the same sockets in multiple calls and it will be safe. The > limitation comes from trying to use the same sockets from multiple > simultaneous threads in other socket APIs (select is the exception, > simultaneous send, recv, or close on the same socket is not supported, > especially in 1.4.1). > > > > In regards to the maxfd question, I think there is a small > misunderstanding. The maxfd parameter in select() is the largest FD in > your input FD_SETs + 1. This is because maxfd is used to iterate through > the FD_SETs provided. It has nothing to do with other threads calling > select() or how many sockets are in the system, but the maximum value of > any FDs in the current select() call. > > > > Joel > > > On Jun 23, 2016, at 03:59 AM, lampo <[email protected]> wrote: > > hello, > can someone help me with multithread problem ? > > we use lwip 1.4.1 in PLC products, and if it live through long time(1 month > for example) testing in industry use, > I will back here to report. > > *our problem* > we use multithread select mode in our system, and it "seems" it's ok till > now(1 days passed), > but I see the doc in rawapi.txt,"/Netconn or Socket Api are not reentrant > at > the control bolck granularity level/" . > so I really cannot figure out if im doing right thing. > > *our application background/restriction* > > a, our system is RTOS based , we need 2 TCP clients(separately connecting > to > 2 TCP servers, i.e., 2 lasers), > 1 TCP server(deal with max of 4 remote clients,i.e.,4 modbus clients ), and > 1 web server. > > b, lwip related thread cannot be in polling mode, for here is already a > polling thread in RTOS and it has "soft real time" requirements. > > c, current lwip version is 1.4.1(we are evaluating 2.0.0) > > d, we need to send data to tcp servers periodically, 10 ms > > *our design/implementation * > > 3 thread has used 'select' , but the same socket is only closed by the > thread who created it. here is details, > > we use 'select' in "user tcp client send thread" ,we first call > 'connect',and then call 'select' to determine whether the socket is > connected correctly or not; if some errors detected in connecting or data > sending, we call 'close' to close the socket. > we use 'select' in "user tcp client receive thread", blocked forever > waiting for data, and call 'recvfrom' if data received, if some errors > detected > in this thread,we don't just clost the socket ,but send message to "user > tcp > client send thread" and tell it to close. > we use 'select' in "user tcp server thread",listening for incoming > requests, > receiving and responding(sending) data. > > *our doubt* > 1、 ‘select’ can be used in multithread or not? if yes, the first param > maxfdp1 of lwip_select() must be set to the total number of sockets in each > thread? > for example,in our situation, maxfdp1 = 2(clients) + 4(remote clients) + > 1(listen socket) in each select? > > 2、is SYS_ARCH_PROTECT must be used in multithread? > > 3、if lwip 1.4.1 does not support the multithread select mode, does lwip > 2.0.0 supports it? > > Thanks a lot ! > > > > -- > View this message in context: > http://lwip.100.n7.nabble.com/LwIP-multithread-select-mode-problems-tp26561.html > Sent from the lwip-users mailing list archive at Nabble.com. > > _______________________________________________ > lwip-users mailing list > [email protected] > https://lists.nongnu.org/mailman/listinfo/lwip-users > > > _______________________________________________ > lwip-users mailing list > [email protected] > https://lists.nongnu.org/mailman/listinfo/lwip-users > > > > _______________________________________________ > lwip-users mailing list > [email protected] > https://lists.nongnu.org/mailman/listinfo/lwip-users >
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