Sockets，Unix域UDP C ++ recvfrom无法填充源地址 [英] Sockets, Unix Domain UDP C++ recvfrom fail to populate the source address
问题描述
我在C ++中尝试使用UDP在Android上创建一个unix域套接字服务器和客户端。
我需要客户端向服务器发送一个消息（hi），从那里服务器需要向客户端发送数据。
我已经成功创建了双方的套接字，我能够从客户端接收服务器上的短消息。然而，recvfrom（..）在服务器上不填充结构sockaddr * src_addr，socklen_t * addrlen参数。使用这些src_addr和addrlen的后续sendto消息明显失败（sendto返回-1）。
下面是服务器的代码：
int serverSocket = socket（PF_LOCAL，SOCK_DGRAM，0）;
int transmitBufferSize = OUTPUT_BUFFER_SIZE;
setsockopt（serverSocket，SOL_SOCKET，SO_SNDBUF，& sendingBufferSize，sizeof（sendingBufferSize））;
struct sockaddr_un server;
memset（& server，0，sizeof server）;
server.sun_family = AF_LOCAL;
// sun_path的第一个字节对于抽象命名空间应该是'\0'
const char * socket_name = SOCKET_NAME;
server.sun_path [0] ='\0';
strcpy（server.sun_path + 1，socket_name）;
socklen_t sockaddr_len = sizeof（server.sun_family）+ strlen（socket_name）+ 1;
if（bind（serverSocket，（struct sockaddr *）& server，sockaddr_len）< 0）{
close（serverSocket）;
printf（无法绑定服务器socket\\\
）;
return -1;
}
printf（ - 套接字路径上的套接字绑定成功％s len％d\\\
，& server.sun_path [1]，sockaddr_len）;
_serverSocket = serverSocket;
稍后我从客户端收到一条消息：
int opcode;
_clientAddressLength = sizeof（struct sockaddr_un）;
int numOfBytes = recvfrom（_serverSocket，_messageBuffer，INPUT_BUFFER，0，（struct sockaddr *）& _clientAddress，& _clientAddressLength）;
if（numOfBytes！= 0）
{
printf（Get a message from client\\\
）;
memcpy（& opcode，_messageBuffer，sizeof（opcode））; //我得到我期望的
}
但是_clientAddress是空的，_clientAddressLength设置为0。
后来
int result = sendto _serverSocket
，sendBuf
，sendBufSize
，0
，（const sockaddr *）& _clientAddress
，_clientAddressLength）;
返回-1
最后感谢Nikolai N Fetissov的链接和一些挖掘我使它的工作。我想在UNIX DOMAIN抽象命名空间套接字上发布一个固定的，100％的双向UDP通信的工作示例。这是此 http的副本：//www.toptip.ca/2013/01/unix-domain-socket-with-abstract-socket.html？m = 1 链接与一个固定的错误。
server.cpp
pre>
#include< sys / socket.h>
#include< sys / un.h>
#include< stdio.h>
#include< string.h>
#include< unistd.h>`
#define SERVER_SOCKET#UdsServer//抽象命名空间的＃替换为＃
int main（void）
{
int socket_fd;
struct sockaddr_un server_address，client_address;
int bytes_received，bytes_sent，integer_buffer;
socklen_t address_length = sizeof（server_address.sun_family）+ strlen（SERVER_SOCKET）;
if（（socket_fd = socket（AF_UNIX，SOCK_DGRAM，0））< 0）
{
perror（server：socket）;
return -1;
}
memset（& server_address，0，sizeof（server_address））;
server_address.sun_family = AF_UNIX;
memcpy（server_address.sun_path，SERVER_SOCKET，sizeof（SERVER_SOCKET）-1）; //路径不是C字符串，不是空转
server_address.sun_path [0] = 0;
if（bind（socket_fd，
（const struct sockaddr *）& server_address，
address_length）< 0）
{
perror server：bind）;
close（socket_fd）;
return -1;
}
for（;;）
{
bytes_received = recvfrom（socket_fd，
& integer_buffer，
sizeof（integer_buffer）
0，
（struct sockaddr *）& client_address，
& address_length）;
if（bytes_received！= sizeof（integer_buffer））
{
printf（Error：recvfrom - ％d.\\\
，bytes_received）;
} else {
printf（received：％d.\\\
，integer_buffer）;
integer_buffer + = 10;
bytes_sent = sendto（socket_fd，
& integer_buffer，
sizeof（integer_buffer），
0，
（struct sockaddr *）& client_address
address_length）;
}
}
close（socket_fd）;
return 0;
}
client.cpp
#include< sys / socket.h>
#include< sys / un.h>
#include< stdio.h>
#include< string.h>
#include< unistd.h>
#define SERVER_SOCKET#UdsServer
#define CLIENT_SOCKET#UdsClient
int main（void）
{
int socket_fd;
struct sockaddr_un server_address，client_address;
int bytes_received，bytes_sent，integer_buffer;
socklen_t address_length = sizeof（server_address.sun_family）+ strlen（CLIENT_SOCKET）;`
if（（socket_fd = socket（AF_UNIX，SOCK_DGRAM，0））< 0）
{
perror（client：socket）;
return -1;
}
memset（& client_address，0，sizeof（client_address））;
client_address.sun_family = AF_UNIX;
memcpy（client_address.sun_path，CLIENT_SOCKET，sizeof（CLIENT_SOCKET）-1）;
client_address.sun_path [0] = 0;
if（bind（socket_fd，
（const struct sockaddr *）& client_address，
address_length）< 0）
{
perror client：bind）;
return -1;
}
memset（& server_address，0，sizeof（server_address））;
server_address.sun_family = AF_UNIX;
memcpy（server_address.sun_path，SERVER_SOCKET，sizeof（SERVER_SOCKET）-1）;
server_address.sun_path [0] = 0;
integer_buffer = 1;
for（;;）
{
bytes_sent = sendto（socket_fd，
& integer_buffer，
sizeof（integer_buffer），
0 ，
（struct sockaddr *）& server_address，
address_length）;
bytes_received = recvfrom（socket_fd，
& integer_buffer，
sizeof（integer_buffer），
0，
（struct sockaddr *）& server_address，
& address_length）;
if（bytes_received！= sizeof（integer_buffer））
{
printf（Error：recvfrom - ％d.\\\
，bytes_received）;
return -1;
}
printf（received：％d\\\
，integer_buffer）;
integer_buffer + = 1;
sleep（10）;
}
close（socket_fd）;
return 0;
}
我希望它有帮助，如果你看到更多的错误，请让我知道
您正在将地址大小参数设置为Internet地址大小 sockaddr_in ，这对于Unix路径太小了。
编辑0：
我相信问题是不是 bind（2） - 客户端套接字，因此它没有名称，因此 recvfrom（2）
尝试此处（客户端需要与服务器名称不同的名称）。
I'm trying to create a unix domain socket server and client on Android in C++, using UDP. I need the client to send one message ("hi") to the server and from there on the server needs to send data to the client. I have successfully created the sockets on both sides, and I am able to receive a short message on the server from the client. However recvfrom(..) on the server does not populate the struct sockaddr *src_addr, socklen_t *addrlen arguments. And a subsequent sendto message using those src_addr and addrlen obviously fail (sendto returns -1).
Here's the code for the server :
int serverSocket = socket(PF_LOCAL, SOCK_DGRAM, 0);
int sendingBufferSize = OUTPUT_BUFFER_SIZE;
setsockopt(serverSocket, SOL_SOCKET, SO_SNDBUF, &sendingBufferSize, sizeof(sendingBufferSize));
struct sockaddr_un server;
memset(&server, 0, sizeof server);
server.sun_family = AF_LOCAL;
// the first byte of sun_path should be '\0' for abstract namespace
const char * socket_name = SOCKET_NAME;
server.sun_path[0] = '\0';
strcpy(server.sun_path + 1, socket_name);
socklen_t sockaddr_len = sizeof(server.sun_family) + strlen(socket_name) + 1;
if (bind(serverSocket, (struct sockaddr *) &server, sockaddr_len) < 0) {
close(serverSocket);
printf("Failed to bind the server socket\n");
return -1;
}
printf("- Socket binding successful on socket path %s len %d\n", &server.sun_path[1], sockaddr_len);
_serverSocket = serverSocket;
And later I receive a message from the client:
int opcode;
_clientAddressLength = sizeof(struct sockaddr_un);
int numOfBytes = recvfrom(_serverSocket, _messageBuffer, INPUT_BUFFER, 0, (struct sockaddr *)&_clientAddress, &_clientAddressLength);
if (numOfBytes != 0)
{
printf("Got a message from client\n");
memcpy(&opcode, _messageBuffer, sizeof(opcode)); // I'm getting what I expected
}
However _clientAddress is empty and _clientAddressLength is set to 0.
And later
int result = sendto(_serverSocket
, sendBuf
, sendBufSize
, 0
, (const sockaddr*)&_clientAddress
, _clientAddressLength);
returns -1
Thanks for your help guys!
EDIT:
Finally thanks to Nikolai N Fetissov's link and some digging I made it work. I'd like to post a fixed, 100% working example of bi-directional UDP communication over UNIX DOMAIN abstract namespace sockets. This is a copy of this http://www.toptip.ca/2013/01/unix-domain-socket-with-abstract-socket.html?m=1 link with a fixed bugs. For the future generations, as there aren't enough examples on this topic on the net.
server.cpp
#include <sys/socket.h>
#include <sys/un.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>`
#define SERVER_SOCKET "#UdsServer" // The # is replaced by 0 for abstract namespace
int main(void)
{
int socket_fd;
struct sockaddr_un server_address, client_address;
int bytes_received, bytes_sent, integer_buffer;
socklen_t address_length = sizeof(server_address.sun_family)+strlen(SERVER_SOCKET );
if ((socket_fd = socket(AF_UNIX, SOCK_DGRAM, 0)) < 0)
{
perror("server: socket");
return -1;
}
memset(&server_address, 0, sizeof(server_address));
server_address.sun_family = AF_UNIX;
memcpy(server_address.sun_path, SERVER_SOCKET,sizeof(SERVER_SOCKET)-1);// the path is not a C string, and is not NULL turminated
server_address.sun_path[0] = 0;
if (bind(socket_fd,
(const struct sockaddr *) &server_address,
address_length) < 0)
{
perror("server: bind");
close(socket_fd);
return -1;
}
for (;;)
{
bytes_received = recvfrom(socket_fd,
&integer_buffer,
sizeof(integer_buffer),
0,
(struct sockaddr *) &client_address,
&address_length);
if(bytes_received != sizeof(integer_buffer))
{
printf("Error: recvfrom - %d.\n", bytes_received);
} else {
printf("received: %d.\n", integer_buffer);
integer_buffer += 10;
bytes_sent = sendto(socket_fd,
&integer_buffer,
sizeof(integer_buffer),
0,
(struct sockaddr *) &client_address,
address_length);
}
}
close(socket_fd);
return 0;
}
client.cpp
#include <sys/socket.h>
#include <sys/un.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#define SERVER_SOCKET "#UdsServer"
#define CLIENT_SOCKET "#UdsClient"
int main(void)
{
int socket_fd;
struct sockaddr_un server_address, client_address;
int bytes_received, bytes_sent, integer_buffer;
socklen_t address_length = sizeof(server_address.sun_family) + strlen(CLIENT_SOCKET);`
if((socket_fd = socket(AF_UNIX, SOCK_DGRAM, 0)) < 0)
{
perror("client: socket");
return -1;
}
memset(&client_address, 0, sizeof(client_address));
client_address.sun_family = AF_UNIX;
memcpy(client_address.sun_path, CLIENT_SOCKET,sizeof(CLIENT_SOCKET )-1 );
client_address.sun_path[0] = 0;
if(bind(socket_fd,
(const struct sockaddr *) &client_address,
address_length) < 0)
{
perror("client: bind");
return -1;
}
memset(&server_address, 0, sizeof(server_address));
server_address.sun_family = AF_UNIX;
memcpy(server_address.sun_path, SERVER_SOCKET,sizeof(SERVER_SOCKET)-1);
server_address.sun_path[0] = 0;
integer_buffer = 1;
for (;;)
{
bytes_sent = sendto(socket_fd,
&integer_buffer,
sizeof(integer_buffer),
0,
(struct sockaddr *) &server_address,
address_length);
bytes_received = recvfrom(socket_fd,
&integer_buffer,
sizeof(integer_buffer),
0,
(struct sockaddr *) &server_address,
&address_length);
if (bytes_received != sizeof(integer_buffer))
{
printf("Error: recvfrom - %d.\n", bytes_received);
return -1;
}
printf("received: %d\n", integer_buffer);
integer_buffer += 1;
sleep(10);
}
close(socket_fd);
return 0;
}
I hope it helps, and if you see more bugs please let me know
You are setting the address size argument to size of Internet address sockaddr_in, which is too small for Unix path.
Edit 0:
I believe the problem is that you are not bind(2)-ing the client socket, so it does not have a name, thus recvfrom(2) returns zero for address length.
Try code from here (the client needs a name different from the server name).
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