小贝子编程

使用c中使用UDP和TCP套接字编程建立连接



我正在尝试在同一代码中建立UDP和TCP连接。我在server.c，transfer.c和client.c中有3个程序。我希望第一个server运行并等待数据；然后 transfer，然后 client。

我所需的结果是，如果我在client中键入消息，它将使用TCP发送到transfer，并且transfer使用TCP将此消息转发到服务器。当server收到消息时，它将检查消息是alpha还是Digit。如果是alpha，则server使用UDP向client发送"这不是数字"消息。如果是数字，它只是使用UDP将相同的消息转发给client。

我能够使用TCP向server发送消息，然后我无法使用UDP向client发送特定消息。知道怎么了？

这是我的代码。这是我的server.c：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/types.h>      
#include <netinet/in.h>
#include <sys/socket.h>
#include <ctype.h>
#define PORTNUM 2400
#define MAXRCVLEN 500
#define SERVER "127.0.0.1" // local server
#define BUFLEN 512  //Max length of buffer
#define PORT 2500   //The port to establish UDP conection
void DieWithError(char *s)
{
perror(s);
exit(1);
}

int main(int argc, char *argv[])
{
char* msg = "HI n"; 
char buffer[MAXRCVLEN + 1];
int len, consocket;
struct sockaddr_in dest;
struct sockaddr_in serv;
int mysocket;
socklen_t socksize = sizeof(struct sockaddr_in);
memset(&serv, 0, sizeof(serv));
serv.sin_family = AF_INET;
serv.sin_addr.s_addr = htonl(INADDR_ANY);
serv.sin_port = htons(PORTNUM);
mysocket = socket(AF_INET, SOCK_STREAM, 0);
bind(mysocket, (struct sockaddr *)&serv, sizeof(struct sockaddr));
///////////////////////////////////////////////////////////
//UDP initialiazation to forward received message to client
struct sockaddr_in si_other;
int s, i, slen=sizeof(si_other), recv_len;
char buf[BUFLEN];
char message[BUFLEN];
int num; //number of messages   
s=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
//creates socket
memset((char *) &si_other, 0, sizeof(si_other));
si_other.sin_family = AF_INET;
si_other.sin_port = htons(PORT);
inet_aton(SERVER , &si_other.sin_addr);

    /*{
        DieWithError("sendto() failed");
    }*/

 ///////////////////////////////////////////////////////////
do{
listen(mysocket, 1);
consocket = accept(mysocket, (struct sockaddr *)&dest, &socksize);
send(consocket, msg, strlen(msg), 0);
    while(len=recv(consocket, buffer, MAXRCVLEN, 0)>0){
            if(strncmp(buffer, "exit", 4) == 0){ 
        break;
    }
           printf("Received: %s ", buffer);
         //checks the received message alpha or digit
            if(isalpha(buf[0])){
        strcpy(buf, "this is not a digit");//sends this message to client 
        //if the message is alphs
        }

           //udp sends function to send the msg using UDP
            if (sendto(s, message, strlen(message) , 0 , (struct sockaddr
   *) &si_other, slen)==-1)
    {
        DieWithError("sendto() failed");
    }
    //clear the buffer
    memset(buf,'', BUFLEN);
  //memset(buffer, 0, strlen(buffer));

    }
  printf("Goodbye !n");
    close(consocket);
}while(consocket);
close(mysocket);
return EXIT_SUCCESS;
}

这是我的transfer.c：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#define PORTNUM1 2300
#define PORTNUM2 2400
#define MAXRCVLEN 500

int main(int argc, char *argv[])
{
char* msg = "HI from Inter-servern"; 
char buffer[MAXRCVLEN + 1];
int len, consocket;
struct sockaddr_in dest;
struct sockaddr_in serv;
struct sockaddr_in client;
int server_socket;
int client_socket;
// For server connection
socklen_t socksize = sizeof(struct sockaddr_in);
memset(&serv, 0, sizeof(serv));
serv.sin_family = AF_INET;
serv.sin_addr.s_addr = htonl(INADDR_ANY);
serv.sin_port = htons(PORTNUM1);
server_socket = socket(AF_INET, SOCK_STREAM, 0);
bind(server_socket, (struct sockaddr *)&serv, sizeof(struct sockaddr));
////////////////////////////////////////////////////////////
//  code for for client connection 
// socket, connect, and recv here
client_socket = socket(AF_INET, SOCK_STREAM, 0);
 memset(&client, 0, sizeof(client));
 client.sin_family = AF_INET;
 client.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
 client.sin_port = htons(PORTNUM2);
 connect(client_socket, (struct sockaddr *)&client, sizeof(struct 
 sockaddr));
recv(client_socket, msg, MAXRCVLEN, 0);
///////////////////////////////////////////////////////////

// printf("As a client, I Received %s n", buffer);
// memset(buffer, 0, strlen(buffer));
printf("Server starts...n");
do{
listen(server_socket, 1);
consocket = accept(server_socket, (struct sockaddr *)&dest, &socksize);
send(consocket, msg, strlen(msg), 0);
    while(len=recv(consocket, buffer, MAXRCVLEN, 0)>0){
            printf("Received: %s ", buffer);
// As a client, send "buffer" here
           send(client_socket, buffer, strlen(buffer), 0);

           if(strncmp(buffer, "exit", 4) == 0) break;

      memset(buffer, 0, strlen(buffer));
       }
printf("Goodbye !n");
    close(consocket);
}while(consocket);
close(client_socket);
close(server_socket);
return EXIT_SUCCESS;
}

这是我的client.c：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <ctype.h>
#define MAXRCVLEN 500
#define PORTNUM 2300
#define BUFLEN 512  //Max length of buffer
#define PORT 2500   //The port  to establish UDP connection
void DieWithError(char *s)
{
    perror(s);
exit(1);
}

int main(int argc, char *argv[])
{
char buffer[MAXRCVLEN + 1]; // for receiving
int len, mysocket;
struct sockaddr_in dest;
char msg[MAXRCVLEN + 1]; // for sending
mysocket = socket(AF_INET, SOCK_STREAM, 0);
memset(&dest, 0, sizeof(dest));
dest.sin_family = AF_INET;
dest.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
dest.sin_port = htons(PORTNUM);
connect(mysocket, (struct sockaddr *)&dest, sizeof(struct sockaddr));
/////////////////////////////////////////////////////////
//UDP initialization 
  struct sockaddr_in si_me, si_other;
  int s, i, slen = sizeof(si_other) , recv_len;
  char message[BUFLEN];
  //int num=0;
  char buf[BUFLEN];
 //create a UDP socket
 if ((s=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1)
{
    DieWithError("socket() failed");
}
// zero out the structure
memset((char *) &si_me, 0, sizeof(si_me));
si_me.sin_family = AF_INET;
si_me.sin_port = htons(PORT);
si_me.sin_addr.s_addr = htonl(INADDR_ANY);
//bind socket to port
if( bind(s , (struct sockaddr*)&si_me, sizeof(si_me) ) == -1)
{
    DieWithError("bind() failed");
}

//check digits or alpha

/////////////////////////////////////////////////////////
len = recv(mysocket, buffer, MAXRCVLEN, 0);
if(len < 0){
    perror("Reciver failed");
    close(mysocket);
    return EXIT_FAILURE;
}
else{
    buffer[len] = '';
    printf("I Received %s n", buffer);
 }

            //printf("Received: %s ", buffer);

 while(1){
    printf("Enter a character ");
    fgets(msg, sizeof(msg), stdin);
    if(strncmp(msg, "exit", 4) == 0) break;
    if(send(mysocket, msg, strlen(msg), 0) < 0){
            perror("Send failed");
            close(mysocket);
            return EXIT_FAILURE;
    }
 memset(msg, 0, strlen(msg));
}
if ((recv_len = recvfrom(s, buf, BUFLEN, 0, (struct sockaddr *) &si_other,
&slen)) == -1 )//to receive message from server as UDP
    {
        DieWithError("recvfrom() failed");
    }
  printf("Received a packet from %s:%dn", inet_ntoa(si_other.sin_addr),
  ntohs(si_other.sin_port));
    printf("Data: %sn" , buf);
 //printf("Received: %s ", buffer);    
 close(mysocket);
return EXIT_SUCCESS;
}

我认为您的编码样式不好。

可以工作。

server.c 

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/types.h>      
#include <netinet/in.h>
#include <sys/socket.h>
#include <ctype.h>
#define PORTNUM 2400
#define MAXRCVLEN 500
#define SERVER "127.0.0.1" // local server
#define BUFLEN 512  //Max length of buffer
#define PORT 2500   //The port to establish UDP conection
void DieWithError(char *s)
{
    perror(s);
    exit(1);
}

int main(int argc, char *argv[])
{
    char* msg = "HI n"; 
    char buffer[MAXRCVLEN + 1];
    int len, consocket;
    struct sockaddr_in dest;
    struct sockaddr_in serv;
    int mysocket;
    socklen_t socksize = sizeof(struct sockaddr_in);
    memset(&serv, 0, sizeof(serv));
    serv.sin_family = AF_INET;
    serv.sin_addr.s_addr = htonl(INADDR_ANY);
    serv.sin_port = htons(PORTNUM);
    mysocket = socket(AF_INET, SOCK_STREAM, 0);
    bind(mysocket, (struct sockaddr *)&serv, sizeof(struct sockaddr));
///////////////////////////////////////////////////////////
//UDP initialiazation to forward received message to client
    struct sockaddr_in si_other;
    int s, i, slen=sizeof(si_other), recv_len;
    char buf[BUFLEN];
    char message[BUFLEN];
    int num; //number of messages   
    s=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
//creates socket
    memset((char *) &si_other, 0, sizeof(si_other));
    si_other.sin_family = AF_INET;
    si_other.sin_port = htons(PORT);
    inet_aton(SERVER , &si_other.sin_addr);

    /*{
        DieWithError("sendto() failed");
    }*/

 ///////////////////////////////////////////////////////////
    do{
        listen(mysocket, 1);
        consocket = accept(mysocket, (struct sockaddr *)&dest, &socksize);
        send(consocket, msg, strlen(msg), 0);
            while((len=recv(consocket, buffer, MAXRCVLEN, 0))>0){
                if( strncmp(buffer, "exit", 4) == 0) 
                    break;
            buffer[len] = '';
                printf("Received: %s", buffer);
         //checks the received message alpha or digit
                memset(buf,0, BUFLEN);
                    if(isalpha(buffer[0])){
                    strcpy(buf, "this is not a digit");//sends this message to client 
        //if the message is alphs
                }
            else {
                    strcpy(buf, "this is a digit");//sends this message to client 
            }
            //puts(buf);
           //udp sends function to send the msg using UDP
                    if (sendto(s, buf, strlen(buf) , 0 , (struct sockaddr*) &si_other, slen)==-1)
                {
                    DieWithError("sendto() failed");
                }
    //clear the buffer
  //memset(buffer, 0, strlen(buffer));
        }
            close(consocket);
    }while(consocket);
    printf("Goodbye !n");
    close(mysocket);
    return EXIT_SUCCESS;
}

Transfer.C 

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <netinet/in.h>
 #include <sys/socket.h>
#define PORTNUM1 2300
#define PORTNUM2 2400
#define MAXRCVLEN 500

int main(int argc, char *argv[])
{
    char* msg = "HI from Inter-servern"; 
    char buffer[MAXRCVLEN + 1];
    int len, consocket;
    struct sockaddr_in dest;
    struct sockaddr_in serv;
    struct sockaddr_in client;
    int server_socket;
    int client_socket;
    // For server connection
    socklen_t socksize = sizeof(struct sockaddr_in);
    memset(&serv, 0, sizeof(serv));
    serv.sin_family = AF_INET;
    serv.sin_addr.s_addr = htonl(INADDR_ANY);
    serv.sin_port = htons(PORTNUM1);
    server_socket = socket(AF_INET, SOCK_STREAM, 0);
    bind(server_socket, (struct sockaddr *)&serv, sizeof(struct sockaddr));
    ////////////////////////////////////////////////////////////
    //  code for for client connection 
    // socket, connect, and recv here
    client_socket = socket(AF_INET, SOCK_STREAM, 0);
    memset(&client, 0, sizeof(client));
    client.sin_family = AF_INET;
    client.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
    client.sin_port = htons(PORTNUM2);
    connect(client_socket, (struct sockaddr *)&client, sizeof(struct sockaddr));
    recv(client_socket, msg, MAXRCVLEN, 0);
    ///////////////////////////////////////////////////////////

    // printf("As a client, I Received %s n", buffer);
    // memset(buffer, 0, strlen(buffer));
    printf("Server starts...n");
    do{
        listen(server_socket, 1);
        consocket = accept(server_socket, (struct sockaddr *)&dest, &socksize);
        send(consocket, msg, strlen(msg), 0);
        while((len=recv(consocket, buffer, MAXRCVLEN, 0))>0){
            printf("Received: %s ", buffer);
    // As a client, send "buffer" here
            send(client_socket, buffer, strlen(buffer), 0);
            if(strncmp(buffer, "exit", 4) == 0) 
                break;
            memset(buffer, 0, strlen(buffer));
        }
        printf("Goodbye !n");
            close(consocket);
    }while(consocket);
    close(client_socket);
    close(server_socket);
    return EXIT_SUCCESS;
}

客户端

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <ctype.h>
#define MAXRCVLEN 500
#define PORTNUM 2300
#define BUFLEN 512  //Max length of buffer
#define PORT 2500   //The port  to establish UDP connection
void DieWithError(char *s)
{
        perror(s);
    exit(1);
}

int main(int argc, char *argv[])
{
    char buffer[MAXRCVLEN + 1]; // for receiving
    int len, mysocket;
    struct sockaddr_in dest;
    char msg[MAXRCVLEN + 1]; // for sending
    mysocket = socket(AF_INET, SOCK_STREAM, 0);
    memset(&dest, 0, sizeof(dest));
    dest.sin_family = AF_INET;
    dest.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
    dest.sin_port = htons(PORTNUM);
    connect(mysocket, (struct sockaddr *)&dest, sizeof(struct sockaddr));
/////////////////////////////////////////////////////////
//UDP initialization 
    struct sockaddr_in si_me, si_other;
    int s, i, recv_len;
    socklen_t slen = sizeof(si_other);
    char message[BUFLEN];
  //int num=0;
    char buf[BUFLEN];
 //create a UDP socket
    if ((s=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1)
    {
            DieWithError("socket() failed");
    }
// zero out the structure
    memset((char *) &si_me, 0, sizeof(si_me));
    si_me.sin_family = AF_INET;
    si_me.sin_port = htons(PORT);
    si_me.sin_addr.s_addr = htonl(INADDR_ANY);
//bind socket to port
    if( bind(s , (struct sockaddr*)&si_me, sizeof(si_me) ) == -1)
    {
            DieWithError("bind() failed");
    }

//check digits or alpha

/////////////////////////////////////////////////////////
    len = recv(mysocket, buffer, MAXRCVLEN, 0);
    if(len < 0){
            perror("Reciver failed");
            close(mysocket);
            return EXIT_FAILURE;
    }
    else{
            buffer[len] = '';
            printf("I Received %s n", buffer);
    }

            //printf("Received: %s ", buffer);

    while(1){
        memset(msg, 0, sizeof(msg));
            printf("Enter a character ");
            fgets(msg, sizeof(msg), stdin);
            if(strncmp(msg, "exit", 4) == 0) 
            ;
            if(send(mysocket, msg, strlen(msg), 0) < 0){
                    perror("Send failed");
                    close(mysocket);
                    return EXIT_FAILURE;
            }
        if ((recv_len = recvfrom(s, buf, BUFLEN, 0, (struct sockaddr *) &si_other, &slen)) == -1 )//to receive message from server as UDP
            {
                DieWithError("recvfrom() failed");
            }
        printf("Received a packet from %s:%dn", inet_ntoa(si_other.sin_addr), ntohs(si_other.sin_port)); 
        printf("Data: %sn" , buf);
    }
 //printf("Received: %s ", buffer);    
    close(mysocket);
    return EXIT_SUCCESS;
}

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