我正在尝试创建一个服务器，该服务器可以从多个连接的客户端接收消息，但是在我的代码中，recv（）函数始终返回-1。如何使我的服务器从客户端接收代码？
这是我的服务器。在底部的while循环中调用recv（）函数。
我尝试使用read（），但是找不到使它解除阻塞的方法。有什么办法可以通过使用read（）来解释它吗？如果没有，即使我连接了新客户端并发送了新消息，如何使用recv（）始终返回-1来解决此问题？
/*------------------Header Files----------------------------------------------------------------------*/
#define _GNU_SOURCE
#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<string.h>
#include<errno.h>
#include<fcntl.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<sys/un.h>
#include<sys/stat.h>
#include<netinet/in.h>
#include<netinet/ip.h>
#include<arpa/inet.h>
/*-------------------Linked List------------------------------------------------------------------------*/
struct client_online{
int client_socket;
char* name;
struct client_online* next;
};
/*-------------------Global Variables-------------------------------------------------------------------*/
struct client_online* first_client = NULL;
/*-------------------Main Function----------------------------------------------------------------------*/
int main(int argc, char* argv[]){
// Cite: get help from office hour code
// Creating the socket
int server_socket;
server_socket = socket(AF_INET, SOCK_STREAM | SOCK_NONBLOCK, 0);
if(server_socket < 0){
perror("Error creating server socket");
return -1;
}
// Server address
struct sockaddr_in server_address;
memset(&server_address, 0, sizeof(struct sockaddr_in));
server_address.sin_family = AF_INET;
server_address.sin_port = htons(atoi(argv[2]));
server_address.sin_addr.s_addr = inet_addr(argv[1]);
// Binding the socket
int binder = bind(server_socket, (const struct sockaddr *) &server_address, sizeof(server_address));
if(binder == -1){
perror("Error calling bind");
return -1;
}
// Listen to the socket
int listener = listen(server_socket, 50);
if(listener == -1){
perror("Error calling listen");
return -1;
}
// Client address
struct sockaddr_in client_address;
// Reading and writing
int quit = 0;
while(!quit){
// Check if there is a new connection
int client_address_size = sizeof(client_address);
int each_client_socket = accept4(server_socket,
(struct sockaddr*) &client_address,
&client_address_size,
SOCK_NONBLOCK);
// If there is a new connection, add client to linked list
if(each_client_socket >= 0){
if(first_client == NULL){
first_client = malloc(sizeof(*first_client));
first_client->client_socket = each_client_socket;
first_client->name = (char*)malloc(100);
strcpy(first_client->name,"User");
first_client->next = NULL;
free(first_client->name);
free(first_client);
}
else{
struct client_online* tracker = first_client;
while(tracker->next != NULL){
tracker = tracker->next;
}
struct client_online* new_client;
new_client = malloc(sizeof(*new_client));
new_client->client_socket = each_client_socket;
new_client->name = (char*)malloc(100);
strcpy(new_client->name, "User");
new_client->next = NULL;
tracker->next = new_client;
free(new_client->name);
free(new_client);
}
}
// Check if there are messages recieved
struct client_online* checker = first_client;
while(checker != NULL){
char client_response[256];
char toSend[256];
bzero(client_response, sizeof(client_response));
int receiver = recv(checker->client_socket,
client_response,
sizeof(client_response),
MSG_DONTWAIT);
printf("%d\n", receiver);
if(receiver > 0){
printf("message received\n");
snprintf(toSend, sizeof(toSend), "%s: %s\n", checker->name, client_response);
struct client_online* sender = first_client;
while(sender != NULL){
send(sender->client_socket, toSend, sizeof(toSend), MSG_DONTWAIT);
}
}
checker = checker->next;
}
sleep(1);
}
return 0;
}
这是我的客户
/*----------------------------------------------------Header Files----------------------------------------*/
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<unistd.h>
#include<fcntl.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<sys/un.h>
#include<sys/stat.h>
#include<netinet/ip.h>
#include<arpa/inet.h>
#define _GNU_SOURCE
/*----------------------------------------------------Main Function--------------------------------------*/
int main(int argc, char* argv[]){
// Seek help from office hour codes
// Create the client socket
int client_socket = socket(AF_INET, SOCK_STREAM, 0);
if(client_socket < 0){
perror("Error creating client socket");
return -1;
}
// Construct the address of the connection
struct sockaddr_in client_address;
memset(&client_address, 0, sizeof(struct sockaddr_in));
client_address.sin_family = AF_INET;
client_address.sin_port = htons(atoi(argv[2]));
client_address.sin_addr.s_addr = inet_addr(argv[1]);
// Connect the client to the server
int connecter = connect(client_socket,
(const struct sockaddr*) &client_address,
sizeof(struct sockaddr_in));
if(connecter < 0){
perror("Error connecting to server");
}
// Reading and writing
int quit = 0;
while(!quit){
// Read from command line
char client_message[256];
memset(&client_message, 0, sizeof(client_message));
int flags = fcntl(STDIN_FILENO, F_GETFL, 0);
fcntl(STDIN_FILENO, F_SETFL, flags | O_NONBLOCK);
int reader = read(STDIN_FILENO, client_message, sizeof(client_message));
if (reader > 0) {
// Writing normal message
send(client_socket, client_message, 1, MSG_WAITALL);
}
//
sleep(1);
}
return 0;
}
答案 0 :(得分：0)
由于您正在将MSG_DONTWAIT传递给您的recv调用，因此，如果尚无来自客户端的消息，则该调用将返回错误以表明这一事实。
如果您使用的是轮询机制，例如epoll，则通常会等待可读的通知。收到通知后，您可以重试recv呼叫。我在您的代码中看不到任何轮询机制。
或者，您可以为每个新连接生成一个线程，并使用对recv的阻塞调用（忽略MSG_DONTWAIT标志）。