我有一个TCP服务器和UDP服务器，在同一个端口上，使用select（）函数为多个客户端提供服务 . 通常，一切都很好，客户端可以与两个服务器通信，但有时，在极少数情况下，我收到错误消息，这是由于非套接字上的recv（）错误套接字操作 . 如果我在这种情况下打印套接字描述符，它通常是1（stdout）或0（stdin） . 所以它应该抛出这个错误，但为什么我的代码首先尝试从那些套接字recv（）是我的问题 .
这是我的代码片段
- TCP套接字创建
// TCP port setup
int sockfd; // listening socket descriptor
int newsockfd; // newly accept()ed socket descriptor
struct sockaddr_storage remoteaddr; // client address
socklen_t addrlen;
char buf_tcp[256]; // buffer for client data
char buf_copy_tcp[256];
int recv_bytes;
char remoteIP[INET6_ADDRSTRLEN];
int yes=1; // for setsockopt() SO_REUSEADDR
int i, k, rv_getaddrinfo, rv_setsockopt, rv_bind, rv_listen, rv_select;
struct addrinfo hints, *servinfo, *ptr;
// get a socket and bind it
memset(&hints, 0, sizeof(hints));
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
hints.ai_flags = AI_PASSIVE;
rv_getaddrinfo = getaddrinfo(NULL, PORT, &hints, &servinfo);
if (rv_getaddrinfo != 0)
{
fprintf(stderr, "CLI Server TCP error: %s\r\n", gai_strerror(rv_getaddrinfo));
exit(1);
}
for(ptr=servinfo; ptr!=NULL; ptr=ptr->ai_next)
{
sockfd = socket(ptr->ai_family, ptr->ai_socktype, ptr->ai_protocol);
if (sockfd == -1)
{
fprintf(stdout, "CLI Server TCP error: socket\r\n");
continue;
}
// lose the pesky "address already in use" error message
rv_setsockopt = setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int));
if(rv_setsockopt == -1)
{
fprintf(stdout, "CLI Server TCP error: setsockopt\r\n");
exit(1);
}
rv_bind = bind(sockfd, ptr->ai_addr, ptr->ai_addrlen);
if (rv_bind == -1)
{
close(sockfd);
fprintf(stdout, "CLI Server TCP error: bind\r\n");
continue;
}
break;
}
// if we got here, it means we didn't get bound
if (ptr == NULL)
{
fprintf(stdout, "CLI Server TCP error: failed to bind\r\n");
exit(2);
}
freeaddrinfo(servinfo); // all done with this
// listen
rv_listen = listen(sockfd, 10);
if (rv_listen == -1)
{
fprintf(stdout, "CLI Server TCP error: listen\r\n");
exit(3);
}
- UDP套接字创建
// UDP port setup
int sockfd_udp; // listening socket descriptor
struct sockaddr_storage remoteaddr_udp; // client address
socklen_t addrlen_udp;
char buf_udp[256]; // buffer for client data
char buf_copy_udp[256];
int recv_bytes_udp;
char remoteIP_udp[INET6_ADDRSTRLEN];
int yes_udp=1; // for setsockopt() SO_REUSEADDR
int j, rv_getaddrinfo_udp, rv_setsockopt_udp, rv_bind_udp;
struct addrinfo hints_udp, *servinfo_udp, *ptr_udp;
// get a socket and bind it
memset(&hints_udp, 0, sizeof(hints_udp));
hints_udp.ai_family = AF_UNSPEC;
hints_udp.ai_socktype = SOCK_DGRAM;
hints_udp.ai_flags = AI_PASSIVE;
rv_getaddrinfo_udp = getaddrinfo(NULL, PORT, &hints_udp, &servinfo_udp);
if (rv_getaddrinfo_udp != 0)
{
fprintf(stderr, "CLI Server UDP error: %s\r\n", gai_strerror(rv_getaddrinfo_udp));
exit(1);
}
for(ptr_udp=servinfo_udp; ptr_udp!=NULL; ptr_udp=ptr_udp->ai_next)
{
sockfd_udp = socket(ptr_udp->ai_family, ptr_udp->ai_socktype, ptr_udp->ai_protocol);
if (sockfd_udp == -1)
{
fprintf(stdout, "CLI Server UDP error: socket\r\n");
continue;
}
// lose the pesky "address already in use" error message
rv_setsockopt_udp = setsockopt(sockfd_udp, SOL_SOCKET, SO_REUSEADDR, &yes_udp, sizeof(int));
if(rv_setsockopt_udp == -1)
{
fprintf(stdout, "CLI Server UDP error: setsockopt\r\n");
exit(1);
}
rv_bind_udp = bind(sockfd_udp, ptr_udp->ai_addr, ptr_udp->ai_addrlen);
if (rv_bind_udp == -1)
{
close(sockfd_udp);
fprintf(stdout, "CLI Server UDP error: bind\r\n");
continue;
}
break;
}
// if we got here, it means we didn't get bound
if (ptr_udp == NULL)
{
fprintf(stdout, "CLI Server UDP error: failed to bind\r\n");
exit(2);
}
freeaddrinfo(servinfo_udp); // all done with this
3.多客户端服务器的select（）函数
struct timeval timeout; // timeout for select(), 1ms
timeout.tv_sec = 0;
timeout.tv_usec = 1000;
fd_set master; // master file descriptor list
fd_set read_fds; // temp file descriptor list for select()
int fdmax; // maximum file descriptor number
FD_ZERO(&master); // clear the master and temp sets
FD_ZERO(&read_fds);
// add the listener to the master set
FD_SET(sockfd, &master);
FD_SET(sockfd_udp, &master);
// keep track of the biggest file descriptor
if(sockfd > sockfd_udp)
fdmax = sockfd; // so far, it's this one
else
fdmax = sockfd_udp; // so far, it's this one
while(1)
{
read_fds = master; // copy it
rv_select = select(fdmax+1, &read_fds, NULL, NULL, &timeout);
if (rv_select == -1)
{
fprintf(stdout, "CLI Server TCP error: select\r\n");
exit(4);
}
// run through the existing connections looking for data to read
for(i=0; i<=fdmax; i++)
{
if (FD_ISSET(i, &read_fds))
{ // we got one!!
if (i == sockfd)
{
// handle new tcp connections
addrlen = sizeof(remoteaddr);
newsockfd = accept(sockfd, (struct sockaddr *)&remoteaddr, &addrlen);
if (newsockfd == -1)
fprintf(stdout, "CLI Server TCP error: accept\r\n");
else
{
FD_SET(newsockfd, &master); // add to master set
if (newsockfd > fdmax) // keep track of the max
fdmax = newsockfd;
inet_ntop(remoteaddr.ss_family, get_in_addr((struct sockaddr*)&remoteaddr), remoteIP, INET6_ADDRSTRLEN);
fprintf(stdout, "CLI Server TCP: new connection from %s on socket %d\r\n", remoteIP, newsockfd);
}
}
else if (i == sockfd_udp)
{
// handle new udp connections
addrlen_udp = sizeof(remoteaddr_udp);
if ((recv_bytes_udp = recvfrom(i, buf_udp, sizeof(buf_udp), 0, (struct sockaddr *)&remoteaddr_udp, &addrlen_udp)) < 0)
fprintf(stdout, "CLI Server UDP error: recvfrom\r\n");
else
{ // handle data from a client
inet_ntop(remoteaddr_udp.ss_family, get_in_addr((struct sockaddr*)&remoteaddr_udp), remoteIP_udp, INET6_ADDRSTRLEN);
for(j=0; j<=recv_bytes_udp; j++)
{
if( (buf_udp[j] == '\r') | (buf_udp[j] == '\n') )
buf_udp[j] = '\0';
}
fprintf(stdout, "CLI Server UDP: received %s from connection %s\r\n", buf_udp, remoteIP_udp);
}
}
else
{ // handle data from a client
if ((recv_bytes = recv(i, buf_tcp, sizeof(buf_tcp), 0)) <= 0)
{ // got error or connection closed by client
if (recv_bytes == 0) // connection closed
fprintf(stdout, "CLI Server TCP: socket %d hung up\r\n", i);
else
fprintf(stdout, "CLI Server TCP error: recv from socket %d\r\n", i);
if(i > sockfd_udp) // temporary fix as recv error occurs on any open file descriptors.
close(i); // bye!
FD_CLR(i, &master); // remove from master set
}
else
{
for(k=0; k<=recv_bytes; k++)
{
if( (buf_tcp[k] == '\r') | (buf_tcp[k] == '\n') )
buf_tcp[k] = '\0';
}
fprintf(stdout, "CLI Server TCP: received %s from socket %d\r\n", buf_tcp, i);
}
} // END handle data from client
} // END got new incoming connection
} // END looping through file descriptors
usleep(2000);
}
在select（）调用之后，我在for循环中运行所有套接字描述符 . 但if（FD_ISSET（））条件应该清除非套接字，如0,1等 . 在while（1）循环中使用FD_SET（）的唯一地方是接受（）新的TCP客户端，那些套接字描述符必须be> TCP套接字描述符，因此不可能在主集中设置0（stdin），1（stdout） . 但他们不知何故 . 为什么我的代码认为它应该从非套接字recv（）然后生成该错误 . 谁在我的select（）主集中设置描述符0和1 .
此错误很少见，但仍然存在 . 在我的早期版本的代码中，当我收到错误时，我关闭（）该套接字描述符 . 所以我关闭了stdin，stdout和其他一些文件描述符（我用open（）创建） . 这搞砸了我的代码所以为了掩盖上面的问题，我使用if（i> sockfd_udp）来关闭（）描述符，这样只关闭客户端套接字描述符（通过accept（）） .
任何人都可以发现问题吗？