TCP Connect error 115 Operation in Progress What is the Cause?
Solution 1
Based on your information:
- You are trying to do a
connect()
to54.x.x.x
- The socket is
non-blocking
- Connection timeout is
60 sec
First, if you look into your /usr/include/asm-generic/errno.h
you'll see the following:
#define EINPROGRESS 115 /* Operation now in progress */
It means an existing operation on the socket is in progress. Since, you said you are doing a connect()
call, lets do a man connect
:
EINPROGRESS The socket is nonblocking and the connection cannot be completed immediately. It is possible to select(2) or poll(2) for completion by selecting the socket for writing. After select(2) indicates writability, use getsockopt(2) to read the SO_ERROR option at level SOL_SOCKET to determine whether connect() completed successfully (SO_ERROR is zero) or unsuccessfully (SO_ERROR is one of the usual error codes listed here, explaining the reason for the failure).
So, the best guess would be that the TCP 3-way handshake (your connect()
call to 54.x.x.x
IP address) is taking longer than expected to complete. Since the connect()
operation is already in progress, any subsequent operation on the socket is resulting into EINPROGRESS
error code. As suggested in the man page, try to use select()
or poll()
to check if your socket is ready to use (to perform read()
or write()
calls).
You can pin-point what is preventing your TCP handshake to complete by capturing and analyzing the traffic to/from your own machine and 54.x.x.x
. The best tool to help you with this is called WireShark. Good luck.
Solution 2
This seems to be the behaviour of connect():
If the connection cannot be established immediately and O_NONBLOCK is set for the file descriptor for the socket, connect() shall fail and set errno to [EINPROGRESS], but the connection request shall not be aborted, and the connection shall be established asynchronously. Subsequent calls to connect() for the same socket, before the connection is established, shall fail and set errno to [EALREADY].
Syed Shamsheer
Updated on December 13, 2020Comments
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Syed Shamsheer over 3 years
My application creats a TCP connection, This is working normaly. But in one network server has many IP say
- 174.X.X.X
- 54.x.x.x like this
When calling TCP connect (Non blocking with timeout of 60 seconds) to IP
174.X.X.X
is always success . But TCP connect to same server with ip54.x.x.x
is failing (most of the times) with errno 115 measn operation in progress.Can you please explain me what are the possible reason for errno 115
OS : Linux
My TCP conenct code is as below
tcp_connect(......) { int iValOpt = 0; int iLength= 0; fcnt((int)(long)SockID,F_SETFL_O_NONBLOCK); ret = connect (sockID,(struct sockaddr*)pstSockAdr,uiSockLen); if (ret < 0) { if (errno == EINPROGRESS) { stTv.tv_sec = 60; stTv.tv_usec = 0; FD_ZERO(&write_fd); FD_SET(sockID,&write_fd); iLength = sizeof(int); if (0 < select (sockID+1) , NULL,&write_fd,NULL,&stTv); { if(0 > getsockopt(sockID,SOL_SOCKET,SO_ERROR,(void*)(&iValOpt),&iLength)) { return -1 } if (0 != iValOpt) { return -1; } return success; } else { return -1; } } else { return -1; } } return success; }
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Syed Shamsheer about 12 yearsMy application is SFTP, user creates many connect to same server with same port 22
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Syed Shamsheer about 12 yearsI have added my Code above , can u please check is any possible errors ? the above code work fine in my netwrok , may be because of my network non-block error EINPROGRESS never occure
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gsbabil about 12 years@user1340512: Try posting clean and complete version of the code so that one can test.
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Syed Shamsheer about 12 yearsThanks for u r reply , I can't post all code here , But I pasted only the code whhere failure is return . The code work fine in our network (may be because in our network non-block error never happen and conenct always success) . I need to know is if EINPROGRESS errno set is above code work fine or before 60 s the abvoe code can return -1