套接字，Unix域UDP C ++ recvfrom无法填充源地址
我试图在C ++上使用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条消息（“hi”），然后服务器上需要向客户端发送数据。 我已经成功创建了双方的套接字，并且能够从客户端接收服务器上的短消息。 但是，服务器上的recvfrom（..）不会填充struct sockaddr * src_addr和socklen_t * addrlen参数。 然后使用这些src_addr和addrlen的后续sendto消息显然失败（sendto返回-1）。
以下是服务器的代码：
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 ' ' for abstract namespace
const char * socket_name = SOCKET_NAME;
server.sun_path[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 socketn");
return -1;
}
printf("- Socket binding successful on socket path %s len %dn", &server.sun_path[1], sockaddr_len);
_serverSocket = serverSocket;
后来我收到客户的一条消息：
int opcode;
_clientAddressLength = sizeof(struct sockaddr_un);
int numOfBytes = recvfrom(_serverSocket, _messageBuffer, INPUT_BUFFER, 0, (struct sockaddr *)&_clientAddress, &_clientAddressLength);
if (numOfBytes != 0)
{
printf("Got a message from clientn");
memcpy(&opcode, _messageBuffer, sizeof(opcode)); // I'm getting what I expected
}
但_clientAddress为空，_clientAddressLength设置为0。
然后
int result = sendto(_serverSocket
, sendBuf
, sendBufSize
, 0
, (const sockaddr*)&_clientAddress
, _clientAddressLength);
返回-1
谢谢你们的帮助！
编辑：
最后感谢Nikolai N Fetissov的链接和一些挖掘工作。 我想通过UNIX DOMAIN抽象名称空间套接字发布一个固定的，100％双向UDP通信的工作示例。 这是一个带有固定错误的http://www.toptip.ca/2013/01/unix-domain-socket-with-abstract-socket.html?m=1链接的副本。 对于后代来说，因为在网络上没有足够的这个话题的例子。
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: %dn", 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
您将地址大小参数设置为Internet地址sockaddr_in大小，对于Unix路径而言太小。
编辑0：
我相信问题是你没有bind(2)客户端套接字，所以它没有名称，因此recvfrom(2)返回地址长度为零。
从这里尝试代码（客户端需要一个与服务器名称不同的名称）。
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