SAP Note 22748 - System log: "Operating system call sendto failed"

Symptom:

The system log contains the following message for every transaction:
"Operating system call sendto failed, error no. 13"
Similar messages appear in the developer trace files dev_disp and dev_w ( is the number of the corresponding work process).

The above error message is usually associated with large drops in performance.

Cause and prerequisites

The error message is generated by c module nixxi.c. According to the operating system header file /usr/include/sys/errno.h, errno=13 (EACCES) means "Permission denied".

Search the /etc/hosts file to find the cause of the error message. Usually, the entry
127.0.0.1 localhost loopback
does not exist or is not defined properly.

Solution
Add the missing "localhost" entry to system file /etc/hosts:
127.0.0.1 localhost loopback

IMPORTANT: Even when the "localhost" entry is obviously there, the above error message can appear when the corresponding line in /etc/hosts cannot be read by the R/3 kernel. This can occur when the /etc/hosts file was modified using an editor that added additional, "invisible" characters (reverse line feed ESC-7, carriage return ESC-13, etc.).