我遇到一些recv（）函数的问题，在C程序中使用线程返回-1。该程序的基础是在一个线程中接收一些请求包，并使第二个线程向所有注册的客户端发送多播。
以下是我服务器的代码：
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <arpa/inet.h>
#include <pthread.h>
#define SERVER_PORT 5654
#define MAX_LINE 256
#define MAX_PENDING 5
/*structure of the packet*/
struct packet{
short type;
char data[MAX_LINE];
};
struct data_packet{
short header;
char data[MAX_LINE];
};
/* structure of Registration Table */
struct registrationTable{
int port;
char name[MAX_LINE];
int req_no;
};
struct global_table{
int sockid;
int reqno;
};
void *join_handler(struct global_table *rec){
int new_s;
struct packet packet_reg;
new_s = rec->sockid;
printf("In thread: %i\n",new_s);
printf("In thread: %i\n",rec->reqno);
if(recv(new_s,&packet_reg,sizeof(packet_reg),0)<0){
printf("\ncouldnt receive first reg packet\n");
exit(1);
}
pthread_exit(NULL);
}
int main(int argc, char* argv[])
{
/* initilizing all of the packets*/
struct packet packet_reg;
struct registrationTable table[10];
struct global_table record[20];
struct sockaddr_in sin;
struct sockaddr_in clientAddr;
char buf[MAX_LINE];
int s, new_s;
int len;
int i;
struct hostent *he;
struct in_addr **addr_list;
pthread_t threads[2];
/* setup passive open */
if((s = socket(PF_INET, SOCK_STREAM, 0)) < 0){
perror("tcpserver: socket");
exit(1);
}
/* build address data structure */
bzero((char*)&sin, sizeof(sin));
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = INADDR_ANY;
sin.sin_port = htons(SERVER_PORT);
if(bind(s,(struct sockaddr *)&sin, sizeof(sin)) < 0){
perror("tcpclient: bind");
exit(1);
}
listen(s, MAX_PENDING);
/* wait for connection, then receive and print text */
while(1){
if((new_s = accept(s, (struct sockaddr *)&clientAddr, &len)) < 0){
perror("tcpserver: accept");
exit(1);
}
/* print the port of the client*/
printf("\n Client's port is %d \n", ntohs(clientAddr.sin_port));
/* receive the first registration packet*/
if(recv(new_s,&packet_reg,sizeof(packet_reg),0)<0){
printf("\ncouldnt receive first reg packet\n");
exit(1);
}
struct global_table client_info;
client_info.sockid = ntohs(clientAddr.sin_port);
client_info.reqno = 1;
pthread_create(&threads[0],NULL,join_handler, &client_info);
}
}
客户端：
#include<stdio.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<netdb.h>
#include<string.h>
#include<stdlib.h>
#include<unistd.h>
#define SERVER_PORT 5654
#define MAX_LINE 256
/*structure of the packet*/
struct packet{
short type;
char data[MAX_LINE];
};
struct data_packet{
short header;
char data[MAX_LINE];
};
int main(int argc, char* argv[])
{
struct packet packet_reg;
struct hostent *hp;
struct sockaddr_in sin;
char *host;
char buf[MAX_LINE];
int s;
int len;
char hostname[1024];
hostname[1023] = '\0';
if(argc == 2){
host = argv[1];
}
else{
fprintf(stderr, "usage:newclient server\n");
exit(1);
}
/* translate host name into peer's IP address */
hp = gethostbyname(host);
if(!hp){
fprintf(stderr, "unkown host: %s\n", host);
exit(1);
}
/* active open */
if((s = socket(PF_INET, SOCK_STREAM, 0)) < 0){
perror("tcpclient: socket");
exit(1);
}
/* build address data structure */
bzero((char*)&sin, sizeof(sin));
sin.sin_family = AF_INET;
bcopy(hp->h_addr, (char *)&sin.sin_addr, hp->h_length);
sin.sin_port = htons(SERVER_PORT);
if(connect(s,(struct sockaddr *)&sin, sizeof(sin)) < 0){
perror("tcpclient: connect");
close(s);
exit(1);
}
/* main loop: get and send lines of text
all you have to do to start the program is
enter any key */
while(fgets(buf, sizeof(buf), stdin)){
/* Find the hostname and print it*/
gethostname(hostname, 1023);
printf("Hostname: %s\n", hostname);
/* populate the info for the first registration packet*/
packet_reg.type = htons(121);
strcpy(packet_reg.data,hostname);
/*send the registration packet to the server*/
if(send(s,&packet_reg,sizeof(packet_reg),0)<0){
printf("\nsend failed\n");
exit(1);
}
/* Print the contents of the first registration packet*/
printf("Sent 1st reg packet data: %s\n",packet_reg.data );
printf("Sent 1st reg packet type: %i\n",ntohs(packet_reg.type));
/* create the second registration packet.
I created separate packets for this so
it was clearer*/
packet_reg.type = htons(121);
strcpy(packet_reg.data,hostname);
/*send the second registration packet to the server*/
if(send(s,&packet_reg,sizeof(packet_reg),0)<0){
printf("\nsend failed\n");
exit(1);
}
/* Print the contents of the second registration packet*/
printf("Sent 2nd reg packet data: %s\n",packet_reg.data );
printf("Sent 2nd reg packet type: %i\n",ntohs(packet_reg.type));
}
}
所以基本上，我正在创建连接并等待接收第一个注册数据包（packet_reg）。这有效，我收到了数据包。然后我将程序的控制权发送给线程。然而，虽然＆＃34; rec＆＃34;变量正确传递信息，后续接收不起作用，并以小于0的值退出。
其他信息：数据包都是正确发送和接收的，但客户端的端口是打印的
printf("\n Client's port is %d \n", ntohs(clientAddr.sin_port));
列为0.我不确定这是否是一个问题，但是当所有接收都在main函数中时，代码工作正常。
另一个问题可能是我收到以下警告：
passing argument 3 pf pthread_create from incompatible pointer type expected 'void * (*) (void *)' but argument of type 'void * (*) (struct global_table*)'
我已经研究过这个警告，并知道它与接收数据无关，然后再进行投射有关。但是，当我从那里打印以检查时，数据正在被正确地发送到线程。
基本上，问题是虽然我可以从线程外部的客户端接收包含相同语句的数据包，但当我在线程内部时，不会收到数据包，并且recv（）返回-1。
答案 0 :(得分：0)
我不小心将接收设置为端口而不是套接字。我是假的。我知道很多人告诉我有关TCP约定的代码构造有多糟糕。我正在为一项作业建立代码，我无法对教授告诉我们这是做到这一点的方法。