CODEWITHSUNDEEP
socketsunixudp
Anonymous
Anonymous

Reputation: 1297

SO_REUSEADDR with UDP datagrams - Resource unavailable

I'm using SO_REUSEADDR option, but I'm not sure why am getting Resource temporary unvailable option.

I'm testing client server code on 127.0.0.1

if ( (sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0 )
{
    perror("socket() error!!\n");
    exit(1);
}

if ( setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof(reuse) ) < 0 ) {
    perror("SO_REUSEADDR failed::");
    exit(1);
}

while(1) {

    nbytes_read = recvfrom(sockfd, (void *)&recvd_msg, sizeof(recvd_msg),
                           flags, &from, &from_len);
    printf("nbytes_read = %d\n", nbytes_read);
    if(nbytes_read == -1) {
        perror("client: recvfrom() failed");
        return FAILED;
    }
    if (nbytes_read > 0) {
        if(recvd_msg.hdr.msgtype == DATA)
            printf("recvd %d bytes from server\n", recvd_msg.hdr.payload_size);
            ftp_show_payload(&recvd_msg);
    }
    if(recvd_msg.hdr.is_last == TRUE) {
        break;
    }
}

Error message: " client: recvfrom() failed: Resource temporarily unavailable"

errno:11

After trying to run client for 3-4 times, I get the data, I'm not sure whats happening.

Also, this problem is on Ubuntu Linux, but when I run the same client server on Solaris, it works fine!!

Upvotes: 1

Views: 4072

Answers (3)

Alam
Alam

Reputation: 1596

SO_REUSEADDR is useful when you use bind(), but here you are not using bind.

I dont see any problem if recvfrom() returns -1

Use bind() and replace your call recvfrom() with recv(). recv() will receive all the packets at the port you used in your bind call.

Upvotes: 1

user207421
user207421

Reputation: 310840

  1. Your test is invalid. recvfrom() can return zero, which doesn't indicate an error. It is only valid to call perror() if you get -1. So you may not have a problem at all ..

  2. I don't see why you're using SO_REUSEADDR at all here, as you're not binding to a specific port.

Upvotes: 0

Ben Jackson
Ben Jackson

Reputation: 93690

Are you trimming out any other socket configuration? EAGAIN is typically returned when you read a non-blocking socket and there's no data available. The manpage for recvfrom lists the possible errnos that will be set on failure with an explanation for each one.

Upvotes: 0

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